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• Data Modeling: Logical Modeling Exercise

  - by swisscheese

  In trying to learn the art of data storage I have been trying to take in as much solid information as possible. PerformanceDBA posted some really helpful tutorials/examples in the following posts among others: is my data normalized? and Relational table naming convention. I already asked a subset question of this model here. So to make sure I understood the concepts he presented and I have seen elsewhere I wanted to take things a step or two further and see if I am grasping the concepts. Hence the purpose of this post, which hopefully others can also learn from. Everything I present is conceptual to me and for learning rather than applying it in some production system. It would be cool to get some input from PerformanceDBA also since I used his models to get started, but I appreciate all input given from anyone. As I am new to databases and especially modeling I will be the first to admit that I may not always ask the right questions, explain my thoughts clearly, or use the right verbage due to lack of expertise on the subject. So please keep that in mind and feel free to steer me in the right direction if I head off track. If there is enough interest in this I would like to take this from the logical to physical phases to show the evolution of the process and share it here on Stack. I will keep this thread for the Logical Diagram though and start new one for the additional steps. For my understanding I will be building a MySQL DB in the end to run some tests and see if what I came up with actually works. Here is the list of things that I want to capture in this conceptual model. Edit for V1.2 The purpose of this is to list Bands, their members, and the Events that they will be appearing at, as well as offer music and other merchandise for sale Members will be able to match up with friends Members can write reviews on the Bands, their music, and their events. There can only be one review per member on a given item, although they can edit their reviews and history will be maintained. BandMembers will have the chance to write a single Comment on Reviews about the Band they are associated with. Collectively as a Band only one Comment is allowed per Review. Members can then rate all Reviews and Comments but only once per given instance Members can select their favorite Bands, music, Merchandise, and Events Bands, Songs, and Events will be categorized into the type of Genre that they are and then further subcategorized into a SubGenre if necessary. It is ok for a Band or Event to fall into more then one Genre/SubGenre combination. Event date, time, and location will be posted for a given band and members can show that they will be attending the Event. An Event can be comprised of more than one Band, and multiple Events can take place at a single location on the same day Every party will be tied to at least one address and address history shall be maintained. Each party could also be tied to more then one address at a time (i.e. billing, shipping, physical) There will be stored profiles for Bands, BandMembers, and general members. So there it is, maybe a bit involved but could be a great learning tool for many hopefully as the process evolves and input is given by the community. Any input? EDIT v1.1 In response to PerformanceDBA U.3) That means no merchandise other than Band merchandise in the database. Correct ? That was my original thought but you got me thinking. Maybe the site would want to sell its own merchandise or even other merchandise from the bands. Not sure a mod to make for that. Would it require an entire rework of the Catalog section or just the identifying relationship that exists with the Band? Attempted a mod to sell both complete albums or song. Either way they would both be in electronic format only available for download. That is why I listed an Album as being comprised of Songs rather then 2 separate entities. U.5) I understand what you bring up about the circular relation with Favorite. I would like to get to this “It is either one Entity with some form of differentiation (FavoriteType) which identifies its treatment” but how to is not clear to me. What am I missing here? u.6) “Business Rules This is probably the only area you are weak in.” Thanks for the honest response. I will readdress these but I hope to clear up some confusion in my head first with the responses I have posted back to you. Q.1) Yes I would like to have Accepted, Rejected, and Blocked. I am not sure what you are referring to as to how this would change the logical model? Q.2) A person does not have to be a User. They can exist only as a BandMember. Is that what you are asking? Minor Issue Zero, One, or More…Oops I admit I forgot to give this attention when building the model. I am submitting this version as is and will address in a future version. I need to read up more on Constraint Checking to make sure I am understanding things. M.4) Depends if you envision OrderPurchase in the future. Can you expand as to what you mean here? EDIT V1.2 In response to PerformanceDBA input... Lessons learned. I was mixing the concept of Identifying / Non-Identifying and Cardinality (i.e. Genre / SubGenre), and doing so inconsistently to make things worse. Associative Tables are not required in Logical Diagrams as their many-to-many relationships can be depicted and then expanded in the Physical Model. I was overlooking the Cardinality in a lot of the relationships The importance of reading through relationships using effective Verb Phrases to reassure I am modeling what I want to accomplish. U.2) In the concept of this model it is only required to track a Venue as a location for an Event. No further data needs to be collected. With that being said Events will take place on a given EventDate and will be hosted at a Venue. Venues will host multiple events and possibly multiple events on a given date. In my new model my thinking was that EventDate is already tied to Event . Therefore, Venue will not need a relationship with EventDate. The 5th and 6th bullets you have listed under U.2) leave me questioning my thinking though. Am I missing something here? U.3) Is it time to move the link between Item and Band up to Item and Party instead? With the current design I don't see a possibility to sell merchandise not tied to the band as you have brought up. U.5) I left as per your input rather than making it a discrete Supertype/Subtype Relationship as I don’t see a benefit of having that type of roll up. Additional Revisions AR.1) After going through the exercise for FavoriteItem, I feel that Item to Review requires a many-to-many relationship so that is indicated. Necessary? Ok here we go for v1.3 I took a few days on this version, going back and forth with my design. Once the logical process is complete, as I want to see if I am on the right track, I will go through in depth what I had learned and the troubles I faced as a beginner going through this process. The big point for this version was it took throwing in some Keys to help see what I was missing in the past. Going through the process of doing a matrix proved to be of great help also. Regardless of anything, if it wasn't for the input given by PerformanceDBA I would still be a lost soul wondering in the dark. Who knows my current design might reaffirm that I still am, but I have learned a lot so I am know I at least have a flashlight in my hand. At this point in time I admit that I am still confused about identifying and non-identifying relationships. In my model I had to use non-identifying relationships with non nulls just to join the relationships I wanted to model. In reading a lot on the subject there seems to be a lot of disagreement and indecisiveness on the subject so I did what I thought represented the right things in my model. When to force (identifying) and when to be free (non-identifying)? Anyone have inputs? EDIT V1.4 Ok took the V1.3 inputs and cleaned things up for this V1.4 Currently working on a V1.5 to include attributes.

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• Understanding and Implementing a Force based graph layout algorithm

  - by zcourts

  I'm trying to implement a force base graph layout algorithm, based on http://en.wikipedia.org/wiki/Force-based_algorithms_(graph_drawing) My first attempt didn't work so I looked at http://blog.ivank.net/force-based-graph-drawing-in-javascript.html and https://github.com/dhotson/springy I changed my implementation based on what I thought I understood from those two but I haven't managed to get it right and I'm hoping someone can help? JavaScript isn't my strong point so be gentle... If you're wondering why write my own. In reality I have no real reason to write my own I'm just trying to understand how the algorithm is implemented. Especially in my first link, that demo is brilliant. This is what I've come up with //support function.bind - https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/bind#Compatibility if (!Function.prototype.bind) { Function.prototype.bind = function (oThis) { if (typeof this !== "function") { // closest thing possible to the ECMAScript 5 internal IsCallable function throw new TypeError("Function.prototype.bind - what is trying to be bound is not callable"); } var aArgs = Array.prototype.slice.call(arguments, 1), fToBind = this, fNOP = function () {}, fBound = function () { return fToBind.apply(this instanceof fNOP ? this : oThis || window, aArgs.concat(Array.prototype.slice.call(arguments))); }; fNOP.prototype = this.prototype; fBound.prototype = new fNOP(); return fBound; }; } (function() { var lastTime = 0; var vendors = ['ms', 'moz', 'webkit', 'o']; for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) { window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame']; window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame']; } if (!window.requestAnimationFrame) window.requestAnimationFrame = function(callback, element) { var currTime = new Date().getTime(); var timeToCall = Math.max(0, 16 - (currTime - lastTime)); var id = window.setTimeout(function() { callback(currTime + timeToCall); }, timeToCall); lastTime = currTime + timeToCall; return id; }; if (!window.cancelAnimationFrame) window.cancelAnimationFrame = function(id) { clearTimeout(id); }; }()); function Graph(o){ this.options=o; this.vertices={}; this.edges={};//form {vertexID:{edgeID:edge}} } /** *Adds an edge to the graph. If the verticies in this edge are not already in the *graph then they are added */ Graph.prototype.addEdge=function(e){ //if vertex1 and vertex2 doesn't exist in this.vertices add them if(typeof(this.vertices[e.vertex1])==='undefined') this.vertices[e.vertex1]=new Vertex(e.vertex1); if(typeof(this.vertices[e.vertex2])==='undefined') this.vertices[e.vertex2]=new Vertex(e.vertex2); //add the edge if(typeof(this.edges[e.vertex1])==='undefined') this.edges[e.vertex1]={}; this.edges[e.vertex1][e.id]=e; } /** * Add a vertex to the graph. If a vertex with the same ID already exists then * the existing vertex's .data property is replaced with the @param v.data */ Graph.prototype.addVertex=function(v){ if(typeof(this.vertices[v.id])==='undefined') this.vertices[v.id]=v; else this.vertices[v.id].data=v.data; } function Vertex(id,data){ this.id=id; this.data=data?data:{}; //initialize to data.[x|y|z] or generate random number for each this.x = this.data.x?this.data.x:-100 + Math.random()*200; this.y = this.data.y?this.data.y:-100 + Math.random()*200; this.z = this.data.y?this.data.y:-100 + Math.random()*200; //set initial velocity to 0 this.velocity = new Point(0, 0, 0); this.mass=this.data.mass?this.data.mass:Math.random(); this.force=new Point(0,0,0); } function Edge(vertex1ID,vertex2ID){ vertex1ID=vertex1ID?vertex1ID:Math.random() vertex2ID=vertex2ID?vertex2ID:Math.random() this.id=vertex1ID+"->"+vertex2ID; this.vertex1=vertex1ID; this.vertex2=vertex2ID; } function Point(x, y, z) { this.x = x; this.y = y; this.z = z; } Point.prototype.plus=function(p){ this.x +=p.x this.y +=p.y this.z +=p.z } function ForceLayout(o){ this.repulsion = o.repulsion?o.repulsion:200; this.attraction = o.attraction?o.attraction:0.06; this.damping = o.damping?o.damping:0.9; this.graph = o.graph?o.graph:new Graph(); this.total_kinetic_energy =0; this.animationID=-1; } ForceLayout.prototype.draw=function(){ //vertex velocities initialized to (0,0,0) when a vertex is created //vertex positions initialized to random position when created cc=0; do{ this.total_kinetic_energy =0; //for each vertex for(var i in this.graph.vertices){ var thisNode=this.graph.vertices[i]; // running sum of total force on this particular node var netForce=new Point(0,0,0) //for each other node for(var j in this.graph.vertices){ if(thisNode!=this.graph.vertices[j]){ //net-force := net-force + Coulomb_repulsion( this_node, other_node ) netForce.plus(this.CoulombRepulsion( thisNode,this.graph.vertices[j])) } } //for each spring connected to this node for(var k in this.graph.edges[thisNode.id]){ //(this node, node its connected to) //pass id of this node and the node its connected to so hookesattraction //can update the force on both vertices and return that force to be //added to the net force this.HookesAttraction(thisNode.id, this.graph.edges[thisNode.id][k].vertex2 ) } // without damping, it moves forever // this_node.velocity := (this_node.velocity + timestep * net-force) * damping thisNode.velocity.x=(thisNode.velocity.x+thisNode.force.x)*this.damping; thisNode.velocity.y=(thisNode.velocity.y+thisNode.force.y)*this.damping; thisNode.velocity.z=(thisNode.velocity.z+thisNode.force.z)*this.damping; //this_node.position := this_node.position + timestep * this_node.velocity thisNode.x=thisNode.velocity.x; thisNode.y=thisNode.velocity.y; thisNode.z=thisNode.velocity.z; //normalize x,y,z??? //total_kinetic_energy := total_kinetic_energy + this_node.mass * (this_node.velocity)^2 this.total_kinetic_energy +=thisNode.mass*((thisNode.velocity.x+thisNode.velocity.y+thisNode.velocity.z)* (thisNode.velocity.x+thisNode.velocity.y+thisNode.velocity.z)) } cc+=1; }while(this.total_kinetic_energy >0.5) console.log(cc,this.total_kinetic_energy,this.graph) this.cancelAnimation(); } ForceLayout.prototype.HookesAttraction=function(v1ID,v2ID){ var a=this.graph.vertices[v1ID] var b=this.graph.vertices[v2ID] var force=new Point(this.attraction*(b.x - a.x),this.attraction*(b.y - a.y),this.attraction*(b.z - a.z)) // hook's attraction a.force.x += force.x; a.force.y += force.y; a.force.z += force.z; b.force.x += this.attraction*(a.x - b.x); b.force.y += this.attraction*(a.y - b.y); b.force.z += this.attraction*(a.z - b.z); return force; } ForceLayout.prototype.CoulombRepulsion=function(vertex1,vertex2){ //http://en.wikipedia.org/wiki/Coulomb's_law // distance squared = ((x1-x2)*(x1-x2)) + ((y1-y2)*(y1-y2)) + ((z1-z2)*(z1-z2)) var distanceSquared = ( (vertex1.x-vertex2.x)*(vertex1.x-vertex2.x)+ (vertex1.y-vertex2.y)*(vertex1.y-vertex2.y)+ (vertex1.z-vertex2.z)*(vertex1.z-vertex2.z) ); if(distanceSquared==0) distanceSquared = 0.001; var coul = this.repulsion / distanceSquared; return new Point(coul * (vertex1.x-vertex2.x),coul * (vertex1.y-vertex2.y), coul * (vertex1.z-vertex2.z)); } ForceLayout.prototype.animate=function(){ if(this.animating) this.animationID=requestAnimationFrame(this.animate.bind(this)); this.draw(); } ForceLayout.prototype.cancelAnimation=function(){ cancelAnimationFrame(this.animationID); this.animating=false; } ForceLayout.prototype.redraw=function(){ this.animating=true; this.animate(); } $(document).ready(function(){ var g= new Graph(); for(var i=0;i<=100;i++){ var v1=new Vertex(Math.random(), {}) var v2=new Vertex(Math.random(), {}) var e1= new Edge(v1.id,v2.id); g.addEdge(e1); } console.log(g); var l=new ForceLayout({ graph:g }); l.redraw(); });

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• problem solving [closed]

  - by Suresh S

  Problem Statement The Sports Associations in India (SAI) wants to choose 2 teams of 4 people each to send to Asian games. There are 13 people who want to be members of the teams. The SAI tries grouping them in various ways to see which athletes perform well together. Each grouping gets one test run on the test track and their time is recorded. Your task is to help the SAI choose two disjoint teams of 4 such that the sum of their practice times is minimal. Input There will be several input instances. The first line of each instance gives the total number of practice runs. This will be followed by n lines. Each of those lines will contain 5 numbers: p1 p2 p3 p4 t t is the time taken (in milliseconds) by the team consisting of p1, p2, p3 and p4. The time taken will not be more than 2 minutes. The end of the input will be indicated by a line with n=0. Output Output the best total and the two teams that you choose. If it is impossible to choose two disjoint teams from the test runs given, output -1. Sample Input 6 1 2 3 4 30000 10 11 12 13 15000 5 6 7 8 37800 1 5 10 12 20000 5 6 9 11 43000 1 9 12 13 11000 3 1 4 7 9 10000 3 5 7 11 17890 6 7 12 13 20000 0 Sample Output 45000 -1 Input to the problem 40 2 8 11 9 15532 1 13 11 9 57629 10 12 1 5 43406 6 10 1 2 43904 8 3 4 11 12473 6 12 5 11 19826 3 9 10 11 48347 6 12 13 1 45854 5 4 9 7 34452 9 8 12 2 5596 4 10 2 7 6778 3 6 8 5 32858 13 12 8 6 42457 12 9 2 5 49530 6 8 10 7 51453 1 3 11 9 18620 6 2 5 11 5153 4 1 9 8 37336 10 5 1 12 59524 4 5 3 2 1318 2 13 6 8 7839 12 4 9 5 30697 4 10 13 1 25249 4 2 9 13 52359 8 11 1 9 36437 7 5 11 6 58522 9 1 12 6 58837 7 6 8 5 37826 13 1 11 3 1841 11 3 5 13 50000 2 8 7 12 10137 1 4 12 5 32558 8 5 6 7 39021 1 7 10 13 5979 9 2 11 6 29661 13 12 9 7 7219 12 1 11 9 37354 5 1 10 9 47948 8 1 2 10 11071 2 11 1 8 3074 80 3 5 8 10 37873 1 2 3 5 27633 10 13 3 11 8645 13 1 9 6 2167 5 11 13 8 30862 8 7 9 6 47591 3 11 13 8 33823 2 13 7 5 36668 12 3 11 6 53711 6 13 3 7 52412 3 6 7 5 3850 1 5 11 12 35483 1 7 6 10 50943 11 3 6 8 40191 12 8 13 7 4529 4 10 5 1 43280 4 12 10 5 35142 12 4 5 10 37242 9 7 13 2 2661 3 9 2 10 453 3 8 12 9 12479 3 10 11 5 30047 9 1 11 2 40883 6 5 1 2 8774 11 7 9 1 37701 8 3 4 6 32970 4 12 7 10 55109 8 11 13 12 44713 2 10 8 5 37763 13 10 12 2 53628 7 2 5 10 53197 3 2 1 11 14916 1 2 3 10 50756 3 13 5 6 6959 10 6 1 4 2948 4 7 13 9 14146 8 13 10 2 16784 3 2 6 5 30337 1 6 7 8 14239 2 6 11 5 13749 12 1 10 5 30827 4 6 11 8 18780 9 10 8 5 6336 7 9 1 3 3101 10 3 4 13 56678 7 6 3 8 8258 11 7 12 6 19046 13 6 9 8 46356 9 5 11 13 56570 9 1 10 5 6193 8 6 9 11 16854 3 7 4 9 53573 8 12 10 1 28135 10 3 8 4 31411 11 1 3 12 34534 8 6 4 13 3527 1 6 10 9 52307 11 7 1 12 2886 12 11 1 6 17659 13 5 6 8 48834 11 2 1 10 52951 3 9 13 7 21054 1 5 11 9 14507 11 5 12 4 42040 1 6 12 7 46414 5 12 3 10 26239 6 10 7 8 40762 8 11 6 10 38538 13 1 10 7 31140 9 10 13 4 34164 13 6 7 12 49696 6 13 3 5 36003 8 9 13 6 58409 3 10 7 9 20693 2 1 11 12 22653 5 8 4 7 49888 5 3 2 11 29911 8 12 6 9 30964 8 3 13 6 23597 4 1 6 7 31657 4 6 8 7 13 33639 13 8 10 3 27863 5 2 1 12 1408 4 11 1 12 59010 63 10 11 9 8 23611 10 8 6 11 12410 4 6 7 9 44390 8 4 1 6 16543 1 2 8 10 37452 11 12 6 13 28968 11 12 2 8 59617 1 9 11 2 28631 11 6 5 1 27251 2 7 10 4 42503 7 8 10 3 13673 9 13 11 7 30308 6 1 12 9 4888 13 1 9 8 19475 8 7 3 5 34187 8 1 12 3 46266 6 10 12 5 32855 3 7 13 1 38427 2 5 13 3 59487 6 11 1 13 2098 1 4 13 6 22239 13 7 12 3 28703 12 3 7 4 32 9 8 2 13 35271 10 13 6 12 36422 12 6 9 8 44303 1 9 13 11 22962 11 13 6 12 39518 5 6 13 11 47909 4 13 1 8 10654 11 8 12 4 31956 7 12 9 13 35923 4 9 3 2 34736 13 2 10 1 22945 7 10 8 13 36947 1 4 12 13 19432 7 12 13 4 48718 9 5 13 11 18827 11 2 1 12 45444 8 12 6 13 33175 4 2 11 13 56186 2 9 3 11 33218 12 13 8 1 50727 13 1 8 2 48138 7 1 5 3 1926 6 4 10 1 40997 11 3 1 4 26033 6 10 13 1 40988 11 12 5 4 25199 4 3 1 10 23498 3 6 12 7 24306 13 10 12 3 53255 3 13 4 12 14517 7 10 9 3 29925 9 11 12 13 28333 3 5 13 6 13602 13 12 9 6 10394 8 4 12 6 57471 9 3 4 7 34723 11 9 5 3 38480 12 9 10 11 48048 4 3 6 7 31884 2 10 4 5 57654 86 1 6 5 13 56577 6 8 2 5 20429 11 13 9 3 2243 3 1 10 12 55231 9 5 7 8 29964 5 11 8 1 29624 6 9 3 1 43055 12 13 10 8 52132 10 8 4 1 5729 7 3 6 8 53097 11 12 7 1 18711 12 7 6 13 44397 10 12 5 7 53574 5 3 4 13 27078 11 2 5 10 43623 3 7 1 8 57350 10 12 4 9 19752 5 13 9 3 59380 4 7 13 6 32575 7 5 6 11 13593 13 7 12 6 38282 13 7 6 2 45430 6 2 5 10 38082 2 11 13 7 53557 10 6 7 13 40461 6 11 7 1 22007 4 7 2 3 22386 9 7 11 10 35337 2 6 11 7 4129 6 13 5 3 31813 1 11 6 9 11749 5 11 8 13 21858 5 12 9 11 2470 13 10 6 11 14503 8 4 1 3 10783 1 10 12 7 47116 11 1 8 10 25034 8 1 4 9 23350 3 10 1 9 56717 13 2 8 12 5825 12 3 13 7 35628 10 6 1 12 26901 2 13 3 5 2775 1 8 9 7 1294 7 13 12 2 48170 11 9 13 1 34311 9 6 3 13 30663 8 3 10 6 5853 1 10 2 4 19880 9 2 3 12 48990 3 7 11 4 51558 8 13 2 4 9698 9 4 5 1 6834 3 4 12 2 20941 11 3 9 7 40108 13 11 2 4 2594 8 9 10 13 12242 1 8 10 5 42413 7 1 11 3 17779 1 5 8 3 6934 4 9 8 11 10235 8 11 10 2 18879 11 4 8 2 12691 9 7 5 2 44947 3 2 5 4 30042 2 7 12 4 27185 6 5 10 1 28695 12 9 1 5 53813 8 12 9 3 24719 6 1 4 11 22716 1 13 10 8 39981 12 11 5 2 22412 6 11 2 4 14457 4 11 5 3 39658 10 11 2 1 33056 1 3 6 9 16958 6 11 12 7 50779 8 10 6 13 24824 7 10 1 13 35692 13 4 8 9 32885 7 6 4 3 10948 4 5 7 1 36875 5 10 6 7 58746 10 7 8 12 39453 8 4 12 1 46674 11 3 1 8 48103 0

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• XSLT 1.0 recursion

  - by DashaLuna

  I'm stuck with recursion, was wondering if anyone can help me out with it. I have <Receipts> and <Deposits> elements, that are not verbose, i.e. that a <Receipts> element doesn't have an attribute to show what <Deposit> it is towards. I need to figure out <Deposits> "still amount due" and when a last receipt towards it was paid if any. I'm trying to do it with the following code: The idea was to take 1st deposit and see if there are receipts. If the deposit isn't fully paid and there are more receipts - call that recorsive function with all the same params except now count in following receipt. If there aren't any more receipts or deposit is payed - process it correctly (add required attributes). Otherwise proceed with 2nd deposit. And so on. However, the XSLT crashes with error message that "a processor stack has overflowed - possible cause is infinite template recursion" I would really appreciate any help/teps... I'm not that great with recursion and can't understand why mine here doesn't work. Thanks! :) <!-- Accumulate all the deposits with @DueAmount attribute --> <xsl:variable name="depositsClassified"> <xsl:call-template name="classifyDeposits"> <!-- a node-list of all Deposits elements ordered by DueDate Acs --> <xsl:with-param name="depositsAll" select="$deposits"/> <xsl:with-param name="depositPrevAmount" select="'0'"/> <!-- a node-list of all Receipts elements ordered by ReceivedDate Acs --> <xsl:with-param name="receiptsAll" select="$receiptsAsc"/> <xsl:with-param name="receiptCount" select="'1'"/> </xsl:call-template> </xsl:variable> <xsl:template name="classifyDeposits"> <xsl:param name="depositsAll"/> <xsl:param name="depositPrevAmount" select="'0'"/> <xsl:param name="receiptsAll"/> <xsl:param name="receiptCount"/> <xsl:if test="$deposits"> <!-- Do required operations for the 1st deposit --> <xsl:variable name="depositFirst" select="$depositsAll[1]"/> <xsl:variable name="receiptSum"> <xsl:choose> <xsl:when test="$receiptsAll"> <xsl:value-of select="sum($receiptsAll[position() &lt;= $receiptCount]/@ActionAmount)"/> </xsl:when> <xsl:otherwise>0</xsl:otherwise> </xsl:choose> </xsl:variable> <xsl:variable name="diff" select="$depositPrevAmount + $depositFirst/@DepositTotalAmount - $receiptSum"/> <xsl:choose> <xsl:when test="$diff &gt; 0 and $receiptCount &lt; $receiptsQuantityOf"> <xsl:call-template name="classifyDeposits"> <xsl:with-param name="depositsAll" select="$depositsAll"/> <xsl:with-param name="depositPrevAmount" select="$depositPrevAmount"/> <xsl:with-param name="receiptsAll" select="$receiptsAll"/> <xsl:with-param name="receiptCount" select="$receiptCount + 1"/> </xsl:call-template> </xsl:when> <xsl:otherwise> <!-- Record changes to the deposit (@DueAmount and receipt ReceivedDate) --> <xsl:apply-templates select="$depositFirst" mode="defineDeposit"> <xsl:with-param name="diff" select="$diff"/> <xsl:with-param name="latestReceiptForDeposit" select="$receiptsAll[position() = $receiptCount]"/> </xsl:apply-templates> <!-- Recursive call to the next deposit --> <xsl:call-template name="classifyDeposits"> <xsl:with-param name="depositsAll" select="$depositsAll[position() &gt; 1]"/> <xsl:with-param name="depositPrevAmount" select="$depositPrevAmount + $depositFirst/@DepositTotalAmount"/> <xsl:with-param name="receiptsAll" select="$receiptsAll"/> <xsl:with-param name="receiptCount" select="'1'"/> </xsl:call-template> </xsl:otherwise> </xsl:choose> </xsl:if> </xsl:template> <!-- Determine deposit's status, due amount and payment received date if any --> <xsl:template match="Deposits" mode="defineDeposit"> <xsl:param name="diff"/> <xsl:param name="latestReceiptForDeposit"/> <xsl:choose> <xsl:when test="$diff &lt;= 0"> <xsl:apply-templates select="." mode="addAttrs"> <xsl:with-param name="status" select="'paid'"/> <xsl:with-param name="dueAmount" select="'0'"/> <xsl:with-param name="receipt" select="$latestReceiptForDeposit"/> </xsl:apply-templates> </xsl:when> <xsl:when test="$diff = ./@DepositTotalAmount"> <xsl:apply-templates select="." mode="addAttrs"> <xsl:with-param name="status" select="'due'"/> <xsl:with-param name="dueAmount" select="$diff"/> </xsl:apply-templates> </xsl:when> <xsl:when test="$diff &lt; ./@DepositTotalAmount"> <xsl:apply-templates select="." mode="addAttrs"> <xsl:with-param name="status" select="'outstanding'"/> <xsl:with-param name="dueAmount" select="$diff"/> <xsl:with-param name="receipt" select="$latestReceiptForDeposit"/> </xsl:apply-templates> </xsl:when> <xsl:otherwise/> </xsl:choose> </xsl:template> <xsl:template match="Deposits" mode="addAttrs"> <xsl:param name="status"/> <xsl:param name="dueAmount"/> <xsl:param name="receipt" select="''"/> <!-- Constract a new MultiDeposits element with required info --> <xsl:copy> <xsl:copy-of select="./@*"/> <xsl:attribute name="Status"><xsl:value-of select="$status"/></xsl:attribute> <xsl:attribute name="DueAmount"><xsl:value-of select="$dueAmount"/></xsl:attribute> <xsl:if test="$receipt"> <xsl:attribute name="latestReceiptDate"> <xsl:value-of select="$receipt/@ActionDate"/> </xsl:attribute> </xsl:if> <xsl:copy-of select="./*"/> </xsl:copy> </xsl:template>

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• NetLogo 4.1 - implementation of a motorway ( Problem creating collision of cars )

  - by user206019

  Hi there, I am trying to create a simulation of motorway and the behaviour of the drivers in NetLogo. I have some questions that I m struggling to solve. Here is my code: globals [ selected-car ;; the currently selected car average-speed ;; average speed of all the cars look-ahead ] turtles-own [ speed ;; the current speed of the car speed-limit ;; the maximum speed of the car (different for all cars) lane ;; the current lane of the car target-lane ;; the desired lane of the car change? ;; true if the car wants to change lanes patience ;; the driver's current patience max-patience ;; the driver's maximum patience ] to setup ca import-drawing "my_road3.png" set-default-shape turtles "car" crt number_of_cars [ setup-cars ] end to setup-cars set color blue set size .9 set lane (random 3) set target-lane (lane + 1) setxy round random-xcor (lane + 1) set heading 90 set speed 0.1 + random 9.9 set speed-limit (((random 11) / 10) + 1) set change? false set max-patience ((random 50) + 10) set patience (max-patience - (random 10)) ;; make sure no two cars are on the same patch loop [ ifelse any? other turtles-here [ fd 1 ] [ stop ] ;if count turtles-here > 1 ; fd 0.1 ;if ; ;ifelse (any? turtles-on neighbors) or (count turtles-here > 1) ;[ ; ifelse (count turtles-here = 1) ; [ if any? turtles-on neighbors ; [ ; if distance min-one-of turtles-on neighbors [distance myself] > 0.9 ; [stop] ; ] ; ] ; [ fd 0.1 ] ;] ;[ stop ] ] end to go drive end to drive ;; first determine average speed of the cars set average-speed ((sum [speed] of turtles) / number_of_cars) ;set-current-plot "Car Speeds" ;set-current-plot-pen "average" ;plot average-speed ;set-current-plot-pen "max" ;plot (max [speed] of turtles) ;set-current-plot-pen "min" ;plot (abs (min [speed] of turtles) ) ;set-current-plot-pen "selected-car" ;plot ([speed] of selected-car) ask turtles [ ifelse (any? turtles-at 1 0) [ set speed ([speed] of (one-of (turtles-at 1 0))) decelerate ] [ ifelse (look-ahead = 2) [ ifelse (any? turtles-at 2 0) [ set speed ([speed] of (one-of turtles-at 2 0)) decelerate ] [ accelerate if count turtles-at 0 1 = 0 and ycor < 2.5 [lt 90 fd 1 rt 90] ] ] [accelerate if count turtles-at 0 1 = 0 and ycor < 2.5 [lt 90 fd 1 rt 90] ] ] if (speed < 0.01) [ set speed 0.01 ] if (speed > speed-limit) [ set speed speed-limit ] ifelse (change? = false) [ signal ] [ change-lanes ] ;; Control for making sure no one crashes. ifelse (any? turtles-at 1 0) and (xcor != min-pxcor - .5) [ set speed [speed] of (one-of turtles-at 1 0) ] [ ifelse ((any? turtles-at 2 0) and (speed > 1.0)) [ set speed ([speed] of (one-of turtles-at 2 0)) fd 1 ] [jump speed] ] ] tick end ;; increase speed of cars to accelerate ;; turtle procedure set speed (speed + (speed-up / 1000)) end ;; reduce speed of cars to decelerate ;; turtle procedure set speed (speed - (slow-down / 1000)) end to signal ifelse (any? turtles-at 1 0) [ if ([speed] of (one-of (turtles-at 1 0))) < (speed) [ set change? true ] ] [ set change? false ] end ;; undergoes search algorithms to change-lanes ;; turtle procedure show ycor ifelse (patience <= 0) [ ifelse (max-patience <= 1) [ set max-patience (random 10) + 1 ] [ set max-patience (max-patience - (random 5)) ] set patience max-patience ifelse (target-lane = 0) [ set target-lane 1 set lane 0 ] [ set target-lane 0 set lane 1 ] ] [ set patience (patience - 1) ] ifelse (target-lane = lane) [ ifelse (target-lane = 0) [ set target-lane 1 set change? false ] [ set target-lane 0 set change? false ] ] [ ifelse (target-lane = 1) [ ifelse (pycor = 2) [ set lane 1 set change? false ] [ ifelse (not any? turtles-at 0 1) [ set ycor (ycor + 1) ] [ ifelse (not any? turtles-at 1 0) [ set xcor (xcor + 1) ] [ decelerate if (speed <= 0) [ set speed 0.1 ] ] ] ] ] [ ifelse (pycor = -2) [ set lane 0 set change? false ] [ ifelse (not any? turtles-at 0 -1) [ set ycor (ycor - 1) ] [ ifelse (not any? turtles-at 1 0) [ set xcor (xcor + 1) ] [ decelerate if (speed <= 0) [ set speed 0.1 ] ] ] ] ] ] end I know its a bit messy because I am using code from other models from the library. I want to know how to create the collision of the cars. I can't think of any idea. As you notice my agent has almost the same size as the patch (I set it to 0.9 so that you can distinguish the space between 2 cars when they are set next to each other and I round the coordinates so that they are set to the centre of the patch). In my accelerate procedure I set my agent to turn left, move 1, turn right in a loop. I want to know if there's a command that lets me make the agent jump from one lane to the other (to the patch next to it on its left) without making it turn and move. And last, if you notice the code i created the car checks the patch that is next to it on the lane on its left and the patch in front of it and the back of it. So if the 3 patches on its left are empty then it can change lane. The fuzzy part is that when i run the setup and I press Go sometimes (not always) the car goes out of the 3 basic lanes. To understand this I have 7 lanes. The middle one which I don't use which is lane 0. Then there are 3 lanes on top of lane 0 and 3 below it. So the code I am using refers to the upper 3 lanes where I set the cars but for some reason some of the cars change lane and go to lane -3 then -2 and so forth. If someone can give me a tip I would really appreciate it. Thank you in advance. Tip: if you want to try this code in netlogo keep in mind that on interface tab I have 2 buttons one setup and one go as well as 3 sliders with names: number_of_cars , speed-up , slow-down.

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• ORDER BY job failed in the Pig script while running EmbeddedPig using Java

  - by C.c. Huang

  I have this following pig script, which works perfectly using grunt shell (stored the results to HDFS without any issues); however, the last job (ORDER BY) failed if I ran the same script using Java EmbeddedPig. If I replace the ORDER BY job by others, such as GROUP or FOREACH GENERATE, the whole script then succeeded in Java EmbeddedPig. So I think it's the ORDER BY which causes the issue. Anyone has any experience with this? Any help would be appreciated! The Pig script: REGISTER pig-udf-0.0.1-SNAPSHOT.jar; user_similarity = LOAD '/tmp/sample-sim-score-results-31/part-r-00000' USING PigStorage('\t') AS (user_id: chararray, sim_user_id: chararray, basic_sim_score: float, alt_sim_score: float); simplified_user_similarity = FOREACH user_similarity GENERATE $0 AS user_id, $1 AS sim_user_id, $2 AS sim_score; grouped_user_similarity = GROUP simplified_user_similarity BY user_id; ordered_user_similarity = FOREACH grouped_user_similarity { sorted = ORDER simplified_user_similarity BY sim_score DESC; top = LIMIT sorted 10; GENERATE group, top; }; top_influencers = FOREACH ordered_user_similarity GENERATE com.aol.grapevine.similarity.pig.udf.AssignPointsToTopInfluencer($1, 10); all_influence_scores = FOREACH top_influencers GENERATE FLATTEN($0); grouped_influence_scores = GROUP all_influence_scores BY bag_of_topSimUserTuples::user_id; influence_scores = FOREACH grouped_influence_scores GENERATE group AS user_id, SUM(all_influence_scores.bag_of_topSimUserTuples::points) AS influence_score; ordered_influence_scores = ORDER influence_scores BY influence_score DESC; STORE ordered_influence_scores INTO '/tmp/cc-test-results-1' USING PigStorage(); The error log from Pig: 12/04/05 10:00:56 INFO pigstats.ScriptState: Pig script settings are added to the job 12/04/05 10:00:56 INFO mapReduceLayer.JobControlCompiler: mapred.job.reduce.markreset.buffer.percent is not set, set to default 0.3 12/04/05 10:00:58 INFO mapReduceLayer.JobControlCompiler: Setting up single store job 12/04/05 10:00:58 INFO jvm.JvmMetrics: Cannot initialize JVM Metrics with processName=JobTracker, sessionId= - already initialized 12/04/05 10:00:58 INFO mapReduceLayer.MapReduceLauncher: 1 map-reduce job(s) waiting for submission. 12/04/05 10:00:58 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same. 12/04/05 10:00:58 INFO input.FileInputFormat: Total input paths to process : 1 12/04/05 10:00:58 INFO util.MapRedUtil: Total input paths to process : 1 12/04/05 10:00:58 INFO util.MapRedUtil: Total input paths (combined) to process : 1 12/04/05 10:00:58 INFO filecache.TrackerDistributedCacheManager: Creating tmp-1546565755 in /var/lib/hadoop-0.20/cache/cchuang/mapred/local/archive/4334795313006396107_361978491_57907159/localhost/tmp/temp1725960134-work-6955502337234509704 with rwxr-xr-x 12/04/05 10:00:58 INFO filecache.TrackerDistributedCacheManager: Cached hdfs://localhost/tmp/temp1725960134/tmp-1546565755#pigsample_854728855_1333645258470 as /var/lib/hadoop-0.20/cache/cchuang/mapred/local/archive/4334795313006396107_361978491_57907159/localhost/tmp/temp1725960134/tmp-1546565755 12/04/05 10:00:58 INFO filecache.TrackerDistributedCacheManager: Cached hdfs://localhost/tmp/temp1725960134/tmp-1546565755#pigsample_854728855_1333645258470 as /var/lib/hadoop-0.20/cache/cchuang/mapred/local/archive/4334795313006396107_361978491_57907159/localhost/tmp/temp1725960134/tmp-1546565755 12/04/05 10:00:58 WARN mapred.LocalJobRunner: LocalJobRunner does not support symlinking into current working dir. 12/04/05 10:00:58 INFO mapred.TaskRunner: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/local/archive/4334795313006396107_361978491_57907159/localhost/tmp/temp1725960134/tmp-1546565755 <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/pigsample_854728855_1333645258470 12/04/05 10:00:58 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/.job.jar.crc <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/.job.jar.crc 12/04/05 10:00:58 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/.job.split.crc <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/.job.split.crc 12/04/05 10:00:59 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/.job.splitmetainfo.crc <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/.job.splitmetainfo.crc 12/04/05 10:00:59 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/.job.xml.crc <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/.job.xml.crc 12/04/05 10:00:59 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/job.jar <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/job.jar 12/04/05 10:00:59 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/job.split <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/job.split 12/04/05 10:00:59 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/job.splitmetainfo <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/job.splitmetainfo 12/04/05 10:00:59 INFO filecache.TrackerDistributedCacheManager: Creating symlink: /var/lib/hadoop-0.20/cache/cchuang/mapred/staging/cchuang402164468/.staging/job_local_0004/job.xml <- /var/lib/hadoop-0.20/cache/cchuang/mapred/local/localRunner/job.xml 12/04/05 10:00:59 INFO mapred.Task: Using ResourceCalculatorPlugin : null 12/04/05 10:00:59 INFO mapred.MapTask: io.sort.mb = 100 12/04/05 10:00:59 INFO mapred.MapTask: data buffer = 79691776/99614720 12/04/05 10:00:59 INFO mapred.MapTask: record buffer = 262144/327680 12/04/05 10:00:59 WARN mapred.LocalJobRunner: job_local_0004 java.lang.RuntimeException: org.apache.hadoop.mapreduce.lib.input.InvalidInputException: Input path does not exist: file:/Users/cchuang/workspace/grapevine-rec/pigsample_854728855_1333645258470 at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.partitioners.WeightedRangePartitioner.setConf(WeightedRangePartitioner.java:139) at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:62) at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:117) at org.apache.hadoop.mapred.MapTask$NewOutputCollector.<init>(MapTask.java:560) at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:639) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:323) at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:210) Caused by: org.apache.hadoop.mapreduce.lib.input.InvalidInputException: Input path does not exist: file:/Users/cchuang/workspace/grapevine-rec/pigsample_854728855_1333645258470 at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.listStatus(FileInputFormat.java:231) at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigFileInputFormat.listStatus(PigFileInputFormat.java:37) at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.getSplits(FileInputFormat.java:248) at org.apache.pig.impl.io.ReadToEndLoader.init(ReadToEndLoader.java:153) at org.apache.pig.impl.io.ReadToEndLoader.<init>(ReadToEndLoader.java:115) at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.partitioners.WeightedRangePartitioner.setConf(WeightedRangePartitioner.java:112) ... 6 more 12/04/05 10:00:59 INFO filecache.TrackerDistributedCacheManager: Deleted path /var/lib/hadoop-0.20/cache/cchuang/mapred/local/archive/4334795313006396107_361978491_57907159/localhost/tmp/temp1725960134/tmp-1546565755 12/04/05 10:00:59 INFO mapReduceLayer.MapReduceLauncher: HadoopJobId: job_local_0004 12/04/05 10:01:04 INFO mapReduceLayer.MapReduceLauncher: job job_local_0004 has failed! Stop running all dependent jobs 12/04/05 10:01:04 INFO mapReduceLayer.MapReduceLauncher: 100% complete 12/04/05 10:01:04 ERROR pigstats.PigStatsUtil: 1 map reduce job(s) failed! 12/04/05 10:01:04 INFO pigstats.PigStats: Script Statistics: HadoopVersion PigVersion UserId StartedAt FinishedAt Features 0.20.2-cdh3u3 0.8.1-cdh3u3 cchuang 2012-04-05 10:00:34 2012-04-05 10:01:04 GROUP_BY,ORDER_BY Some jobs have failed! Stop running all dependent jobs Job Stats (time in seconds): JobId Maps Reduces MaxMapTime MinMapTIme AvgMapTime MaxReduceTime MinReduceTime AvgReduceTime Alias Feature Outputs job_local_0001 0 0 0 0 0 0 0 0 all_influence_scores,grouped_user_similarity,simplified_user_similarity,user_similarity GROUP_BY job_local_0002 0 0 0 0 0 0 0 0 grouped_influence_scores,influence_scores GROUP_BY,COMBINER job_local_0003 0 0 0 0 0 0 0 0 ordered_influence_scores SAMPLER Failed Jobs: JobId Alias Feature Message Outputs job_local_0004 ordered_influence_scores ORDER_BY Message: Job failed! Error - NA /tmp/cc-test-results-1, Input(s): Successfully read 0 records from: "/tmp/sample-sim-score-results-31/part-r-00000" Output(s): Failed to produce result in "/tmp/cc-test-results-1" Counters: Total records written : 0 Total bytes written : 0 Spillable Memory Manager spill count : 0 Total bags proactively spilled: 0 Total records proactively spilled: 0 Job DAG: job_local_0001 -> job_local_0002, job_local_0002 -> job_local_0003, job_local_0003 -> job_local_0004, job_local_0004 12/04/05 10:01:04 INFO mapReduceLayer.MapReduceLauncher: Some jobs have failed! Stop running all dependent jobs

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• Criticize my code, please

  - by Micky

  Hey, I was applying for a position, and they asked me to complete a coding problem for them. I did so and submitted it, but I later found out I was rejected from the position. Anyways, I have an eclectic programming background so I'm not sure if my code is grossly wrong or if I just didn't have the best solution out there. I would like to post my code and get some feedback about it. Before I do, here's a description of a problem: You are given a sorted array of integers, say, {1, 2, 4, 4, 5, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 11, 13 }. Now you are supposed to write a program (in C or C++, but I chose C) that prompts the user for an element to search for. The program will then search for the element. If it is found, then it should return the first index the entry was found at and the number of instances of that element. If the element is not found, then it should return "not found" or something similar. Here's a simple run of it (with the array I just put up): Enter a number to search for: 4 4 was found at index 2. There are 2 instances for 4 in the array. Enter a number to search for: -4. -4 is not in the array. They made a comment that my code should scale well with large arrays (so I wrote up a binary search). Anyways, my code basically runs as follows: Prompts user for input. Then it checks if it is within bounds (bigger than a[0] in the array and smaller than the largest element of the array). If so, then I perform a binary search. If the element is found, then I wrote two while loops. One while loop will count to the left of the element found, and the second while loop will count to the right of the element found. The loops terminate when the adjacent elements do not match with the desired value. EX: 4, 4, 4, 4, 4 The bold 4 is the value the binary search landed on. One loop will check to the left of it, and another loop will check to the right of it. Their sum will be the total number of instances of the the number four. Anyways, I don't know if there are any advanced techniques that I am missing or if I just don't have the CS background and made a big error. Any constructive critiques would be appreciated! #include <stdio.h> #include <stdlib.h> #include <string.h> #include <stddef.h> /* function prototype */ int get_num_of_ints( const int* arr, size_t r, int N, size_t* first, size_t* count ); int main() { int N; /* input variable */ int arr[]={1,1,2,3,3,4,4,4,4,5,5,7,7,7,7,8,8,8,9,11,12,12}; /* array of sorted integers */ size_t r = sizeof(arr)/sizeof(arr[0]); /* right bound */ size_t first; /* first match index */ size_t count; /* total number of matches */ /* prompts the user to enter input */ printf( "\nPlease input the integer you would like to find.\n" ); scanf( "%d", &N ); int a = get_num_of_ints( arr, r, N, &first, &count ); /* If the function returns -1 then the value is not found. Else it is returned */ if( a == -1) printf( "%d has not been found.\n", N ); else if(a >= 0){ printf( "The first matching index is %d.\n", first ); printf( "The total number of instances is %d.\n", count ); } return 0; } /* function definition */ int get_num_of_ints( const int* arr, size_t r, int N, size_t* first, size_t* count ) { int lo=0; /* lower bound for search */ int m=0; /* middle value obtained */ int hi=r-1; /* upper bound for search */ int w=r-1; /* used as a fixed upper bound to calculate the number of right instances of a particular value. */ /* binary search to find if a value exists */ /* first check if the element is out of bounds */ if( N < arr[0] || arr[hi] < N ){ m = -1; } else{ /* binary search to find a value, if it exists, within given parameters */ while(lo <= hi){ m = (hi + lo)/2; if(arr[m] < N) lo = m+1; else if(arr[m] > N) hi = m-1; else if(arr[m]==N){ m=m; break; } } if (lo > hi) /* if it doesn't we assign it -1 */ m = -1; } /* If the value is found, then we compute the left and right instances of it */ if( m >= 0 ){ int j = m-1; /* starting with the first term to the left */ int L = 0; /* total number of left instances */ /* while loop computes total number of left instances */ while( j >= 0 && arr[j] == arr[m] ){ L++; j--; } /* There are six possible outcomes of this. Depending on the outcome, we must assign the first index variable accordingly */ if( j > 0 && L > 0 ) *first=j+1; else if( j==0 && L==0) *first=m; else if( j > 0 && L==0 ) *first=m; else if(j < 0 && L==0 ) *first=m; else if( j < 0 && L > 0 ) *first=0; else if( j=0 && L > 0 ) *first=j+1; int h = m + 1; /* starting with the first term to the right */ int R = 0; /* total number of right instances */ /* while loop computes total number of right instances */ /* we fixed w earlier so that it's value does not change */ while( arr[h]==arr[m] && h <= w ){ R++; h++; } *count = (R + L + 1); /* total number of instances stored as value of count */ return *first; /* first instance index stored here */ } /* if value does not exist, then we return a negative value */ else if( m==-1) return -1; }

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• questions regarding the use of A* with the 15-square puzzle

  - by Cheeso

  I'm trying to build an A* solver for a 15-square puzzle. The goal is to re-arrange the tiles so that they appear in their natural positions. You can only slide one tile at a time. Each possible state of the puzzle is a node in the search graph. For the h(x) function, I am using an aggregate sum, across all tiles, of the tile's dislocation from the goal state. In the above image, the 5 is at location 0,0, and it belongs at location 1,0, therefore it contributes 1 to the h(x) function. The next tile is the 11, located at 0,1, and belongs at 2,2, therefore it contributes 3 to h(x). And so on. EDIT: I now understand this is what they call "Manhattan distance", or "taxicab distance". I have been using a step count for g(x). In my implementation, for any node in the state graph, g is just +1 from the prior node's g. To find successive nodes, I just examine where I can possibly move the "hole" in the puzzle. There are 3 neighbors for the puzzle state (aka node) that is displayed: the hole can move north, west, or east. My A* search sometimes converges to a solution in 20s, sometimes 180s, and sometimes doesn't converge at all (waited 10 mins or more). I think h is reasonable. I'm wondering if I've modeled g properly. In other words, is it possible that my A* function is reaching a node in the graph via a path that is not the shortest path? Maybe have I not waited long enough? Maybe 10 minutes is not long enough? For a fully random arrangement, (assuming no parity problems), What is the average number of permutations an A* solution will examine? (please show the math) I'm going to look for logic errors in my code, but in the meantime, Any tips? (ps: it's done in Javascript). Also, no, this isn't CompSci homework. It's just a personal exploration thing. I'm just trying to learn Javascript. EDIT: I've found that the run-time is highly depend upon the heuristic. I saw the 10x factor applied to the heuristic from the article someone mentioned, and it made me wonder - why 10x? Why linear? Because this is done in javascript, I could modify the code to dynamically update an html table with the node currently being considered. This allowd me to peek at the algorithm as it was progressing. With a regular taxicab distance heuristic, I watched as it failed to converge. There were 5's and 12's in the top row, and they kept hanging around. I'd see 1,2,3,4 creep into the top row, but then they'd drop out, and other numbers would move up there. What I was hoping to see was 1,2,3,4 sort of creeping up to the top, and then staying there. I thought to myself - this is not the way I solve this personally. Doing this manually, I solve the top row, then the 2ne row, then the 3rd and 4th rows sort of concurrently. So I tweaked the h(x) function to more heavily weight the higher rows and the "lefter" columns. The result was that the A* converged much more quickly. It now runs in 3 minutes instead of "indefinitely". With the "peek" I talked about, I can see the smaller numbers creep up to the higher rows and stay there. Not only does this seem like the right thing, it runs much faster. I'm in the process of trying a bunch of variations. It seems pretty clear that A* runtime is very sensitive to the heuristic. Currently the best heuristic I've found uses the summation of dislocation * ((4-i) + (4-j)) where i and j are the row and column, and dislocation is the taxicab distance. One interesting part of the result I got: with a particular heuristic I find a path very quickly, but it is obviously not the shortest path. I think this is because I am weighting the heuristic. In one case I got a path of 178 steps in 10s. My own manual effort produce a solution in 87 moves. (much more than 10s). More investigation warranted. So the result is I am seeing it converge must faster, and the path is definitely not the shortest. I have to think about this more. Code: var stop = false; function Astar(start, goal, callback) { // start and goal are nodes in the graph, represented by // an array of 16 ints. The goal is: [1,2,3,...14,15,0] // Zero represents the hole. // callback is a method to call when finished. This runs a long time, // therefore we need to use setTimeout() to break it up, to avoid // the browser warning like "Stop running this script?" // g is the actual distance traveled from initial node to current node. // h is the heuristic estimate of distance from current to goal. stop = false; start.g = start.dontgo = 0; // calcHeuristic inserts an .h member into the array calcHeuristicDistance(start); // start the stack with one element var closed = []; // set of nodes already evaluated. var open = [ start ]; // set of nodes to evaluate (start with initial node) var iteration = function() { if (open.length==0) { // no more nodes. Fail. callback(null); return; } var current = open.shift(); // get highest priority node // update the browser with a table representation of the // node being evaluated $("#solution").html(stateToString(current)); // check solution returns true if current == goal if (checkSolution(current,goal)) { // reconstructPath just records the position of the hole // through each node var path= reconstructPath(start,current); callback(path); return; } closed.push(current); // get the set of neighbors. This is 3 or fewer nodes. // (nextStates is optimized to NOT turn directly back on itself) var neighbors = nextStates(current, goal); for (var i=0; i<neighbors.length; i++) { var n = neighbors[i]; // skip this one if we've already visited it if (closed.containsNode(n)) continue; // .g, .h, and .previous get assigned implicitly when // calculating neighbors. n.g is nothing more than // current.g+1 ; // add to the open list if (!open.containsNode(n)) { // slot into the list, in priority order (minimum f first) open.priorityPush(n); n.previous = current; } } if (stop) { callback(null); return; } setTimeout(iteration, 1); }; // kick off the first iteration iteration(); return null; }

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• making query from different related tables using codeigniter

  - by fatemeh karam

  I'm using codeigniter as i mentioned this is a part of my view code foreach($projects_query as $row)// $row indicates the projects { ?> <tr><td><h3><button type="submit" class="button red-gradient glossy" name = "project_click" > <?php echo $row->txtTaskName; ?></button></h3></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr> <?php foreach($tasks_query as $row2) { // if( $row->txtTaskName == "TestProject") if($row->intTaskID == $row2->intInside)// intInside indicades that the current task($row2) is the subset of which task (system , subsystem or project) { if($row2->intSummary == 0)//if the task(the system) is an executable task & doesn't have any subtask: { $query_team_user_id = $this->admin_in_out_model->get_user_team_task_query($row2->intTaskID);//runs the function and generates a query from tbl_userteamtask where intTaskID equals to the selected row's intTaskID foreach($query_team_user_id as $row_teamid) { $query_teamname = $this->admin_in_out_model->get_team_name($row_teamid->intTeamID); $query_fn_ln = $this->admin_in_out_model->get_fn_ln_from_userid($row_teamid->intUserID); foreach($query_teamname as $row_teamname) {?> <tr><td></td><td></td><td><h4> <?php echo $row2->txtTaskName;?></h4></td> <td><b><font color='#F33558'><?php echo $row_teamname->txtTeamName;?></font></b></td> <?php } foreach($query_fn_ln as $row_f_l_name) {?> <td> <?php echo $row_f_l_name->txtFirstname." ".$row_f_l_name->txtLastname;?></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td> <?php }?> </tr> <?php } } else{ ?> <tr><td></td><td></td><td><h4> <?php echo $row2->txtTaskName;?></h4></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><?php } foreach($tasks_query as $row_subsystems) { if($row_subsystems->intInside == $row2->intTaskID )//if the task is the subtask of a system(it means the task is a subsystem) { if($row_subsystems->intSummary == 0)//if the task is an executable task & doesn't have any subtask: { $query_team_user_id = $this->admin_in_out_model->get_user_team_task_query($row_subsystems->intTaskID); foreach($query_team_user_id as $row_teamid) {?> <tr><?php $query_teamname = $this->admin_in_out_model->get_team_name($row_teamid->intTeamID); $query_fn_ln = $this->admin_in_out_model->get_fn_ln_from_userid($row_teamid->intUserID); foreach($query_teamname as $row_teamname) {?> <td></td><td></td><td><h5><?php echo $row_subsystems->txtTaskName?></h5><br/></td> <td><b><font color='#F33558'><?php echo $row_teamname->txtTeamName;?></font></b></td><?php } foreach($query_fn_ln as $row_f_l_name) {?> <td><?php echo $row_f_l_name->txtFirstname." ".$row_f_l_name->txtLastname;?></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><?php }?> </tr><?php } } else{ ?><tr><td></td><td></td><td><h5><?php echo $row_subsystems->txtTaskName?></h5></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><?php } foreach($tasks_query as $row_tasks) { if($row_tasks->intInside == $row_subsystems->intTaskID )//if the task is the subtask of a subsystem { if($row_tasks->intSummary == 0)//if the task is an executable task & doesn't have any subtask: { $query_team_user_id = $this->admin_in_out_model->get_user_team_task_query($row_tasks->intTaskID); foreach($query_team_user_id as $row_teamid) {?> <tr><?php $query_teamname = $this->admin_in_out_model->get_team_name($row_teamid->intTeamID); $query_fn_ln = $this->admin_in_out_model->get_fn_ln_from_userid($row_teamid->intUserID); foreach($query_teamname as $row_teamname) {?> <td></td><td></td><td><b><?php echo $row_tasks->txtTaskName;?></b></td> <td><b><font color='#F33558'><?php echo $row_teamname->txtTeamName;?></font></b></td><?php } foreach($query_fn_ln as $row_f_l_name) {?> <td><?php echo $row_f_l_name->txtFirstname." ".$row_f_l_name->txtLastname;?></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><?php }?> </tr><?php } } } } } } } } }?> and in controller i have $projects_query = $this->admin_in_out_model->get_projects(); $tasks_query = $this->admin_in_out_model->get_systems(); $userteamtask = $this->admin_in_out_model->get_user_team_task(); $data['tasks_query'] = $tasks_query; $data['projects_query'] = $projects_query; $this->load->view('project_view',$data); but as you see I'm calling my model functions within the view how can i do something else to do this i mean not calling my model function in my view I have to add that, my model function have parameters these are the model functions: function get_projects() { $this -> db -> select('*'); $this -> db -> from('tbl_task'); $this -> db -> where('intInside','0'); $query = $this->db->get(); return $query->result(); } function get_systems() { $this -> db -> select('*'); $this -> db -> from('tbl_task '); $this -> db -> where('intInside <> ','0'); $query = $this->db->get(); return $query->result(); } function get_user_team_task_query($task_id)//gets information from tbl_userteamtask where the field intTaskID is equal to $task_id { $this -> db -> select('*'); $this -> db -> from('tbl_userteamtask'); $this -> db -> where('intTaskID',$task_id); $query_teamid = $this->db->get(); return $query_teamid->result(); } function get_user_team_task()//gets information from tbl_userteamtask where the field intTaskID is equal to $task_id { $this -> db -> select('*'); $this -> db -> from('tbl_userteamtask'); // $this -> db -> where('intTaskID',$task_id); $query_teamid = $this->db->get(); return $query_teamid->result(); } function get_team_name($query_teamid) { $this -> db -> select('*'); $this -> db -> from('tbl_team'); $this -> db -> where('intTeamID',$query_teamid); $query_teamname = $this->db->get(); return $query_teamname->result(); } function get_user_name($query_userid) { $this -> db -> select('*'); $this -> db -> from('tbl_user'); $this -> db -> where('intUserID',$query_userid); $query_username = $this->db->get(); return $query_username->result(); } function get_fn_ln_from_userid($selected_id) { $this -> db -> select('tbl_user.intUserID, tbl_user.intPersonID,tbl_person.intPersonID,tbl_person.txtFirstname, tbl_person.txtLastname'); $this -> db -> from('tbl_user , tbl_person'); $where = "tbl_user.intPersonID = tbl_person.intPersonID "; $this -> db -> where($where); $this -> db -> where('tbl_user.intUserID', $selected_id); $query = $this -> db -> get();//makes query from DB return $query->result(); } do I have to use subquery ? is this true? i mean can i do this? foreach( $data as $key => $each ) { $data[$key]['team_id'] = $this->get_user_team_task_query( $each['intTaskID'] ); foreach($data[$key]['team_id'] as $key_teamname => $each) { $data[$key_teamname]['team_name'] = $this->get_team_name( $each['intTeamID'] ); } } the model code: foreach( $data as $key => $each ) { $data[$key]['intTaskID'] = $each['intTaskID']; $data[$key]['team_id'] = $this->get_user_team_task_query( $each['intTaskID'] ); foreach($data[$key]['team_id'] as $key => $each) { $data[$key]['team_name'] = $this->get_team_name( $each['intTeamID'] ); #fetching of the teamname and saving in the array $data[$key]['user_name'] = $this->get_fn_ln_from_userid( $each['intUserID'] ); foreach($data[$key]['user_name'] as $key => $each) { $data[$key]['first_name'] = $each['txtFirstname'] ; $data[$key]['last_name'] = $each['txtLastname'] ; } $data[$key]['first_name'] = $data[$key]['first_name']; $data[$key]['last_name'] = $data[$key]['last_name']; } }

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• Problem with java and conditional (game of life)

  - by Muad'Dib

  Hello everybody, I'm trying to implement The Game of Life in java, as an exercise to learn this language. Unfortunately I have a problem, as I don't seem able to make this program run correctly. I implemented a torodial sum (the plane is a donut) with no problem: int SumNeighbours (int i, int j) { int value = 0; value = world[( i - 1 + row ) % row][( j - 1 + column ) % column]+world[( i - 1 + row ) % row][j]+world[( i - 1 + row ) % row][( j + 1 ) % column]; value = value + world[i][( j - 1 + column ) % column] + world[i][( j + 1 ) % column]; value = value + world[( i + 1 ) % row][( j - 1 + column ) % column] + world[( i + 1 ) % row][j]+world[ ( i+1 ) % row ][( j + 1 ) % column]; return value; } And it sums correctly when I test it: void NextWorldTest () { int count; int [][] nextWorld = new int[row][row]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); } System.out.println(); } world=nextWorld; } Unfortunately when I add the conditions of game of life (born/death) the program stop working correctly, as it seems not able anymore to count correctly the alive cells in the neighborhood. It counts where there are none, and it doesn't count when there are some. E.g.: it doesn't count the one below some living cells. It's a very odd behaviour, and it's been giving me a headache for 3 days now... maybe I'm missing something basic about variables? Here you can find the class. void NextWorld () { int count; int [][] nextWorld = new int[row][column]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); if ( ( world[i][j] == 0) && ( count == 3 ) ) { nextWorld[i][j] = 1; } else if ( ( world[i][j] == 1 ) && ( (count == 3) || (count == 2) )) { nextWorld[i][j] = 1; } else { nextWorld[i][j]=0; } } System.out.println(); } world=nextWorld; } } Am I doing something wrong? Below you can find the full package. package com.GaOL; public class GameWorld { int [][] world; int row; int column; public int GetRow() { return row; } public int GetColumn() { return column; } public int GetWorld (int i, int j) { return world[i][j]; } void RandomGen (int size, double p1) { double randomCell; row = size; column = size; world = new int[row][column]; for (int i = 0; i<row; i++ ) { for (int j = 0; j<column; j++ ) { randomCell=Math.random(); if (randomCell < 1-p1) { world[i][j] = 0; } else { world[i][j] = 1; } } } } void printToConsole() { double test = 0; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { if ( world[i][j] == 0 ) { System.out.print(" "); } else { System.out.print(" * "); test++; } } System.out.println(""); } System.out.println("ratio is " + test/(row*column)); } int SumNeighbours (int i, int j) { int value = 0; value = world[( i - 1 + row ) % row][( j - 1 + column ) % column]+world[( i - 1 + row ) % row][j]+world[( i - 1 + row ) % row][( j + 1 ) % column]; value = value + world[i][( j - 1 + column ) % column] + world[i][( j + 1 ) % column]; value = value + world[( i + 1 ) % row][( j - 1 + column ) % column] + world[( i + 1 ) % row][j]+world[ ( i+1 ) % row ][( j + 1 ) % column]; return value; } void NextWorldTest () { int count; int [][] nextWorld = new int[row][row]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); } System.out.println(); } world=nextWorld; } void NextWorld () { int count; int [][] nextWorld = new int[row][column]; nextWorld = world; for (int i=0; i<row; i++) { for (int j=0; j<column; j++) { count = SumNeighbours(i,j); System.out.print(" " + count + " "); if ( ( world[i][j] == 0) && ( count == 3 ) ) { nextWorld[i][j] = 1; } else if ( ( world[i][j] == 1 ) && ( (count == 3) || (count == 2) )) { nextWorld[i][j] = 1; } else { nextWorld[i][j]=0; } } System.out.println(); } world=nextWorld; } } and here the test class: package com.GaOL; public class GameTestClass { public static void main(String[] args) { GameWorld prova = new GameWorld(); prova.RandomGen(10, 0.02); for (int i=0; i<3; i++) { prova.printToConsole(); prova.NextWorld(); } } }

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• Linux (NAS) Permissions problem (Permission Denied)

  - by calumbrodie

  This is probably easier to show than to explain... -bash-3.2$ id uid=501(admin) gid=503(admin) groups=100(users),501(admins),503(admin) -bash-3.2$ groups admin users admins -bash-3.2$ ls -l total 8 drwxrwxrwx 78 admin www 4096 Dec 9 09:02 Inbox drwxrwxrwx 21 admin www 4096 Dec 8 21:45 Movies drwxrwx--- 3 admin www 52 Dec 9 07:57 TV -bash-3.2$ cd Movies -bash-3.2$ ls -l total 20 drwxrwx--- 7 admin www 4096 Dec 8 00:04 Action drwxrwx--- 6 admin www 4096 Dec 8 00:05 Animation drwxrwx--- 4 admin www 4096 Dec 8 00:17 Comedy drwxrwx--- 4 admin www 4096 Dec 8 00:14 Drama drwxrwx--- 4 admin www 4096 Dec 8 00:14 Family drwxrwx--- 6 admin www 58 Dec 6 19:10 Foreign Language drwxrwx--- 2 admin www 31 Dec 7 23:58 Horror drwxrwx--- 3 admin www 50 Dec 8 00:15 Science Fiction drwxrwx--- 2 admin www 6 Dec 8 00:16 Thriller -bash-3.2$ cd ../Inbox -bash: cd: ../Inbox: Permission denied Filesystem is XFS. Are there permissions on the directories that ls -l wouldn't show? I'm the owner of all directories and files inside them. I can sudo to modify the file permissions or view the contents of the folders but I need them to be accessible by 'admin'. Any ideas? I'll be checking the question regularly so let me know if I need to update this with more information. Thanks Edit : Added strace execve("/bin/ls", ["ls", "Inbox"], [/* 21 vars */]) = 0 brk(0) = 0x26000 uname({sys="Linux", node="axentraserver.the-brodie-stora.mystora.com", ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4001c000 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY) = 3 fstat64(3, {st_mode=S_IFREG|0644, st_size=17972, ...}) = 0 mmap2(NULL, 17972, PROT_READ, MAP_PRIVATE, 3, 0) = 0x4001d000 close(3) = 0 open("/lib/librt.so.1", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0P\25\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=39776, ...}) = 0 mmap2(NULL, 57816, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x40025000 mprotect(0x4002b000, 28672, PROT_NONE) = 0 mmap2(0x40032000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x5) = 0x40032000 close(3) = 0 open("/lib/libacl.so.1", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\0\24\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=134375, ...}) = 0 mmap2(NULL, 54368, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x40034000 mprotect(0x4003a000, 28672, PROT_NONE) = 0 mmap2(0x40041000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x5) = 0x40041000 close(3) = 0 open("/lib/libselinux.so.1", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\2147\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=297439, ...}) = 0 mmap2(NULL, 117504, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x40042000 mprotect(0x40056000, 28672, PROT_NONE) = 0 mmap2(0x4005d000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x13) = 0x4005d000 close(3) = 0 open("/lib/libgcc_s.so.1", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\10\"\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=43164, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40022000 mmap2(NULL, 74572, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x4005f000 mprotect(0x4006a000, 28672, PROT_NONE) = 0 mmap2(0x40071000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xa) = 0x40071000 close(3) = 0 open("/lib/libc.so.6", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0XI\1\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=1517948, ...}) = 0 mmap2(NULL, 1245628, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x40072000 mprotect(0x40195000, 32768, PROT_NONE) = 0 mmap2(0x4019d000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x123) = 0x4019d000 mmap2(0x401a0000, 8636, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x401a0000 close(3) = 0 open("/lib/libpthread.so.0", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\230A\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=121044, ...}) = 0 mmap2(NULL, 115184, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x401a3000 mprotect(0x401b5000, 28672, PROT_NONE) = 0 mmap2(0x401bc000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x11) = 0x401bc000 mmap2(0x401be000, 4592, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x401be000 close(3) = 0 open("/lib/libattr.so.1", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\364\f\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=40571, ...}) = 0 mmap2(NULL, 45512, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x401c0000 mprotect(0x401c3000, 32768, PROT_NONE) = 0 mmap2(0x401cb000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3) = 0x401cb000 close(3) = 0 open("/lib/libdl.so.2", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\254\10\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=15344, ...}) = 0 mmap2(NULL, 41116, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x401cc000 mprotect(0x401ce000, 28672, PROT_NONE) = 0 mmap2(0x401d5000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1) = 0x401d5000 close(3) = 0 open("/lib/libsepol.so.1", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\330/\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=228044, ...}) = 0 mmap2(NULL, 301748, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x401d7000 mprotect(0x4020f000, 28672, PROT_NONE) = 0 mmap2(0x40216000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x37) = 0x40216000 mmap2(0x40217000, 39604, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x40217000 close(3) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40221000 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40222000 set_tls(0x40221d00, 0x40221d00, 0x40024000, 0x402223e8, 0x41) = 0 mprotect(0x401d5000, 4096, PROT_READ) = 0 mprotect(0x401bc000, 4096, PROT_READ) = 0 mprotect(0x4019d000, 8192, PROT_READ) = 0 mprotect(0x4005d000, 4096, PROT_READ) = 0 mprotect(0x40032000, 4096, PROT_READ) = 0 mprotect(0x40023000, 4096, PROT_READ) = 0 munmap(0x4001d000, 17972) = 0 set_tid_address(0x402218a8) = 9539 set_robust_list(0x402218b0, 0xc) = 0 rt_sigaction(SIGRTMIN, {0x401a6d90, [], SA_SIGINFO|0x4000000}, NULL, 8) = 0 rt_sigaction(SIGRT_1, {0x401a6c64, [], SA_RESTART|SA_SIGINFO|0x4000000}, NULL, 8) = 0 rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0 getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM_INFINITY}) = 0 brk(0) = 0x26000 brk(0x47000) = 0x47000 open("/proc/mounts", O_RDONLY|O_LARGEFILE) = 3 fstat64(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4001d000 read(3, "rootfs / rootfs rw 0 0\nubi0:root"..., 1024) = 1024 read(3, "fs.xino,noplink,create=mfs,sum,b"..., 1024) = 428 read(3, "", 1024) = 0 close(3) = 0 munmap(0x4001d000, 4096) = 0 access("/etc/selinux/", F_OK) = 0 open("/etc/selinux/config", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory) ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 ioctl(1, TIOCGWINSZ, {ws_row=52, ws_col=153, ws_xpixel=918, ws_ypixel=728}) = 0 stat64("Inbox", {st_mode=S_IFDIR|0777, st_size=4096, ...}) = 0 socket(PF_FILE, SOCK_STREAM, 0) = 3 fcntl64(3, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory) close(3) = 0 socket(PF_FILE, SOCK_STREAM, 0) = 3 fcntl64(3, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory) close(3) = 0 open("/etc/nsswitch.conf", O_RDONLY) = 3 fstat64(3, {st_mode=S_IFREG|0644, st_size=1696, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4001d000 read(3, "#\n# /etc/nsswitch.conf\n#\n# An ex"..., 4096) = 1696 read(3, "", 4096) = 0 close(3) = 0 munmap(0x4001d000, 4096) = 0 open("/etc/ld.so.cache", O_RDONLY) = 3 fstat64(3, {st_mode=S_IFREG|0644, st_size=17972, ...}) = 0 mmap2(NULL, 17972, PROT_READ, MAP_PRIVATE, 3, 0) = 0x4001d000 close(3) = 0 open("/lib/libnss_files.so.2", O_RDONLY) = 3 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\304\27\0\0004\0\0\0"..., 512) = 512 fstat64(3, {st_mode=S_IFREG|0755, st_size=49256, ...}) = 0 mmap2(NULL, 70316, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x40223000 mprotect(0x4022c000, 28672, PROT_NONE) = 0 mmap2(0x40233000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8) = 0x40233000 close(3) = 0 mprotect(0x40233000, 4096, PROT_READ) = 0 munmap(0x4001d000, 17972) = 0 open("/etc/passwd", O_RDONLY) = 3 fcntl64(3, F_GETFD) = 0 fcntl64(3, F_SETFD, FD_CLOEXEC) = 0 fstat64(3, {st_mode=S_IFREG|0644, st_size=1661, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4001d000 read(3, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 1661 close(3) = 0 munmap(0x4001d000, 4096) = 0 socket(PF_FILE, SOCK_STREAM, 0) = 3 fcntl64(3, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory) close(3) = 0 socket(PF_FILE, SOCK_STREAM, 0) = 3 fcntl64(3, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory) close(3) = 0 open("/etc/group", O_RDONLY) = 3 fcntl64(3, F_GETFD) = 0 fcntl64(3, F_SETFD, FD_CLOEXEC) = 0 fstat64(3, {st_mode=S_IFREG|0644, st_size=700, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4001d000 read(3, "root:x:0:root\nbin:x:1:root,bin,d"..., 4096) = 700 close(3) = 0 munmap(0x4001d000, 4096) = 0 open("Inbox", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = -1 EACCES (Permission denied) write(2, "ls: ", 4ls: ) = 4 write(2, "Inbox", 5Inbox) = 5 write(2, ": Permission denied", 19: Permission denied) = 19 write(2, "\n", 1 ) = 1 close(1) = 0 exit_group(2) = ? 2nd edit: Elaboration for Mike. The Inbox sits at the following location /home/admin/MyLibrary/MyVideos/Inbox /home/admin/MyLibrary/MyVideos/Movies The system is a Netgear Stora NAS box that I have root access to. The /home/ folder is mounted as an smb share on various computers around the house. The folder /Inbox cannot be opened on any of those machines (they all connect as 'admin'). When I ssh into the box using the 'admin' credentials I am also unable to access the folder. The folder was created via a Web Admin page hosted on the NAS. The user/group for the Inbox folder was previously apache:www (expected as this folder was created by the web application), but I chmod/chowned the folder as the root user in an attempt to grant the admin user (therefore the rest of the connected machines) access to the files. Sorry for not including this earlier, I wasn't sure if it was relevant and didn't want to confuse the situation. -Thanks 3rd Edit Sorry again - It looks like this NAS is running some custom version of Red Hat, not Debian as previously stated - I'm not sure if this makes a difference

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• SQLite, python, unicode, and non-utf data

  - by Nathan Spears

  I started by trying to store strings in sqlite using python, and got the message: sqlite3.ProgrammingError: You must not use 8-bit bytestrings unless you use a text_factory that can interpret 8-bit bytestrings (like text_factory = str). It is highly recommended that you instead just switch your application to Unicode strings. Ok, I switched to Unicode strings. Then I started getting the message: sqlite3.OperationalError: Could not decode to UTF-8 column 'tag_artist' with text 'Sigur Rós' when trying to retrieve data from the db. More research and I started encoding it in utf8, but then 'Sigur Rós' starts looking like 'Sigur Rós' note: My console was set to display in 'latin_1' as @John Machin pointed out. What gives? After reading this, describing exactly the same situation I'm in, it seems as if the advice is to ignore the other advice and use 8-bit bytestrings after all. I didn't know much about unicode and utf before I started this process. I've learned quite a bit in the last couple hours, but I'm still ignorant of whether there is a way to correctly convert 'ó' from latin-1 to utf-8 and not mangle it. If there isn't, why would sqlite 'highly recommend' I switch my application to unicode strings? I'm going to update this question with a summary and some example code of everything I've learned in the last 24 hours so that someone in my shoes can have an easy(er) guide. If the information I post is wrong or misleading in any way please tell me and I'll update, or one of you senior guys can update. Summary of answers Let me first state the goal as I understand it. The goal in processing various encodings, if you are trying to convert between them, is to understand what your source encoding is, then convert it to unicode using that source encoding, then convert it to your desired encoding. Unicode is a base and encodings are mappings of subsets of that base. utf_8 has room for every character in unicode, but because they aren't in the same place as, for instance, latin_1, a string encoded in utf_8 and sent to a latin_1 console will not look the way you expect. In python the process of getting to unicode and into another encoding looks like: str.decode('source_encoding').encode('desired_encoding') or if the str is already in unicode str.encode('desired_encoding') For sqlite I didn't actually want to encode it again, I wanted to decode it and leave it in unicode format. Here are four things you might need to be aware of as you try to work with unicode and encodings in python. The encoding of the string you want to work with, and the encoding you want to get it to. The system encoding. The console encoding. The encoding of the source file Elaboration: (1) When you read a string from a source, it must have some encoding, like latin_1 or utf_8. In my case, I'm getting strings from filenames, so unfortunately, I could be getting any kind of encoding. Windows XP uses UCS-2 (a Unicode system) as its native string type, which seems like cheating to me. Fortunately for me, the characters in most filenames are not going to be made up of more than one source encoding type, and I think all of mine were either completely latin_1, completely utf_8, or just plain ascii (which is a subset of both of those). So I just read them and decoded them as if they were still in latin_1 or utf_8. It's possible, though, that you could have latin_1 and utf_8 and whatever other characters mixed together in a filename on Windows. Sometimes those characters can show up as boxes, other times they just look mangled, and other times they look correct (accented characters and whatnot). Moving on. (2) Python has a default system encoding that gets set when python starts and can't be changed during runtime. See here for details. Dirty summary ... well here's the file I added: \# sitecustomize.py \# this file can be anywhere in your Python path, \# but it usually goes in ${pythondir}/lib/site-packages/ import sys sys.setdefaultencoding('utf_8') This system encoding is the one that gets used when you use the unicode("str") function without any other encoding parameters. To say that another way, python tries to decode "str" to unicode based on the default system encoding. (3) If you're using IDLE or the command-line python, I think that your console will display according to the default system encoding. I am using pydev with eclipse for some reason, so I had to go into my project settings, edit the launch configuration properties of my test script, go to the Common tab, and change the console from latin-1 to utf-8 so that I could visually confirm what I was doing was working. (4) If you want to have some test strings, eg test_str = "ó" in your source code, then you will have to tell python what kind of encoding you are using in that file. (FYI: when I mistyped an encoding I had to ctrl-Z because my file became unreadable.) This is easily accomplished by putting a line like so at the top of your source code file: # -*- coding: utf_8 -*- If you don't have this information, python attempts to parse your code as ascii by default, and so: SyntaxError: Non-ASCII character '\xf3' in file _redacted_ on line 81, but no encoding declared; see http://www.python.org/peps/pep-0263.html for details Once your program is working correctly, or, if you aren't using python's console or any other console to look at output, then you will probably really only care about #1 on the list. System default and console encoding are not that important unless you need to look at output and/or you are using the builtin unicode() function (without any encoding parameters) instead of the string.decode() function. I wrote a demo function I will paste into the bottom of this gigantic mess that I hope correctly demonstrates the items in my list. Here is some of the output when I run the character 'ó' through the demo function, showing how various methods react to the character as input. My system encoding and console output are both set to utf_8 for this run: '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Now I will change the system and console encoding to latin_1, and I get this output for the same input: 'ó' = original char <type 'str'> repr(char)='\xf3' 'ó' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Notice that the 'original' character displays correctly and the builtin unicode() function works now. Now I change my console output back to utf_8. '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' '?' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Here everything still works the same as last time but the console can't display the output correctly. Etc. The function below also displays more information that this and hopefully would help someone figure out where the gap in their understanding is. I know all this information is in other places and more thoroughly dealt with there, but I hope that this would be a good kickoff point for someone trying to get coding with python and/or sqlite. Ideas are great but sometimes source code can save you a day or two of trying to figure out what functions do what. Disclaimers: I'm no encoding expert, I put this together to help my own understanding. I kept building on it when I should have probably started passing functions as arguments to avoid so much redundant code, so if I can I'll make it more concise. Also, utf_8 and latin_1 are by no means the only encoding schemes, they are just the two I was playing around with because I think they handle everything I need. Add your own encoding schemes to the demo function and test your own input. One more thing: there are apparently crazy application developers making life difficult in Windows. #!/usr/bin/env python # -*- coding: utf_8 -*- import os import sys def encodingDemo(str): validStrings = () try: print "str =",str,"{0} repr(str) = {1}".format(type(str), repr(str)) validStrings += ((str,""),) except UnicodeEncodeError as ude: print "Couldn't print the str itself because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print ude try: x = unicode(str) print "unicode(str) = ",x validStrings+= ((x, " decoded into unicode by the default system encoding"),) except UnicodeDecodeError as ude: print "ERROR. unicode(str) couldn't decode the string because the system encoding is set to an encoding that doesn't understand some character in the string." print "\tThe system encoding is set to {0}. See error:\n\t".format(sys.getdefaultencoding()), print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the unicode(str) because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('latin_1') print "str.decode('latin_1') =",x validStrings+= ((x, " decoded with latin_1 into unicode"),) try: print "str.decode('latin_1').encode('utf_8') =",str.decode('latin_1').encode('utf_8') validStrings+= ((x, " decoded with latin_1 into unicode and encoded into utf_8"),) except UnicodeDecodeError as ude: print "The string was decoded into unicode using the latin_1 encoding, but couldn't be encoded into utf_8. See error:\n\t", print ude except UnicodeDecodeError as ude: print "Something didn't work, probably because the string wasn't latin_1 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('latin_1') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('utf_8') print "str.decode('utf_8') =",x validStrings+= ((x, " decoded with utf_8 into unicode"),) try: print "str.decode('utf_8').encode('latin_1') =",str.decode('utf_8').encode('latin_1') except UnicodeDecodeError as ude: print "str.decode('utf_8').encode('latin_1') didn't work. The string was decoded into unicode using the utf_8 encoding, but couldn't be encoded into latin_1. See error:\n\t", validStrings+= ((x, " decoded with utf_8 into unicode and encoded into latin_1"),) print ude except UnicodeDecodeError as ude: print "str.decode('utf_8') didn't work, probably because the string wasn't utf_8 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('utf_8') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t",uee print print "Printing information about each character in the original string." for char in str: try: print "\t'" + char + "' = original char {0} repr(char)={1}".format(type(char), repr(char)) except UnicodeDecodeError as ude: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), ude) except UnicodeEncodeError as uee: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), uee) print uee try: x = unicode(char) print "\t'" + x + "' = unicode(char) {1} repr(unicode(char))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = unicode(char) ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = unicode(char) {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('latin_1') print "\t'" + x + "' = char.decode('latin_1') {1} repr(char.decode('latin_1'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('latin_1') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('latin_1') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('utf_8') print "\t'" + x + "' = char.decode('utf_8') {1} repr(char.decode('utf_8'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('utf_8') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('utf_8') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) print x = 'ó' encodingDemo(x) Much thanks for the answers below and especially to @John Machin for answering so thoroughly.

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• SQLite, python, unicode, and non-utf data

  - by Nathan Spears

  I started by trying to store strings in sqlite using python, and got the message: sqlite3.ProgrammingError: You must not use 8-bit bytestrings unless you use a text_factory that can interpret 8-bit bytestrings (like text_factory = str). It is highly recommended that you instead just switch your application to Unicode strings. Ok, I switched to Unicode strings. Then I started getting the message: sqlite3.OperationalError: Could not decode to UTF-8 column 'tag_artist' with text 'Sigur Rós' when trying to retrieve data from the db. More research and I started encoding it in utf8, but then 'Sigur Rós' starts looking like 'Sigur Rós' note: My console was set to display in 'latin_1' as @John Machin pointed out. What gives? After reading this, describing exactly the same situation I'm in, it seems as if the advice is to ignore the other advice and use 8-bit bytestrings after all. I didn't know much about unicode and utf before I started this process. I've learned quite a bit in the last couple hours, but I'm still ignorant of whether there is a way to correctly convert 'ó' from latin-1 to utf-8 and not mangle it. If there isn't, why would sqlite 'highly recommend' I switch my application to unicode strings? I'm going to update this question with a summary and some example code of everything I've learned in the last 24 hours so that someone in my shoes can have an easy(er) guide. If the information I post is wrong or misleading in any way please tell me and I'll update, or one of you senior guys can update. Summary of answers Let me first state the goal as I understand it. The goal in processing various encodings, if you are trying to convert between them, is to understand what your source encoding is, then convert it to unicode using that source encoding, then convert it to your desired encoding. Unicode is a base and encodings are mappings of subsets of that base. utf_8 has room for every character in unicode, but because they aren't in the same place as, for instance, latin_1, a string encoded in utf_8 and sent to a latin_1 console will not look the way you expect. In python the process of getting to unicode and into another encoding looks like: str.decode('source_encoding').encode('desired_encoding') or if the str is already in unicode str.encode('desired_encoding') For sqlite I didn't actually want to encode it again, I wanted to decode it and leave it in unicode format. Here are four things you might need to be aware of as you try to work with unicode and encodings in python. The encoding of the string you want to work with, and the encoding you want to get it to. The system encoding. The console encoding. The encoding of the source file Elaboration: (1) When you read a string from a source, it must have some encoding, like latin_1 or utf_8. In my case, I'm getting strings from filenames, so unfortunately, I could be getting any kind of encoding. Windows XP uses UCS-2 (a Unicode system) as its native string type, which seems like cheating to me. Fortunately for me, the characters in most filenames are not going to be made up of more than one source encoding type, and I think all of mine were either completely latin_1, completely utf_8, or just plain ascii (which is a subset of both of those). So I just read them and decoded them as if they were still in latin_1 or utf_8. It's possible, though, that you could have latin_1 and utf_8 and whatever other characters mixed together in a filename on Windows. Sometimes those characters can show up as boxes, other times they just look mangled, and other times they look correct (accented characters and whatnot). Moving on. (2) Python has a default system encoding that gets set when python starts and can't be changed during runtime. See here for details. Dirty summary ... well here's the file I added: \# sitecustomize.py \# this file can be anywhere in your Python path, \# but it usually goes in ${pythondir}/lib/site-packages/ import sys sys.setdefaultencoding('utf_8') This system encoding is the one that gets used when you use the unicode("str") function without any other encoding parameters. To say that another way, python tries to decode "str" to unicode based on the default system encoding. (3) If you're using IDLE or the command-line python, I think that your console will display according to the default system encoding. I am using pydev with eclipse for some reason, so I had to go into my project settings, edit the launch configuration properties of my test script, go to the Common tab, and change the console from latin-1 to utf-8 so that I could visually confirm what I was doing was working. (4) If you want to have some test strings, eg test_str = "ó" in your source code, then you will have to tell python what kind of encoding you are using in that file. (FYI: when I mistyped an encoding I had to ctrl-Z because my file became unreadable.) This is easily accomplished by putting a line like so at the top of your source code file: # -*- coding: utf_8 -*- If you don't have this information, python attempts to parse your code as ascii by default, and so: SyntaxError: Non-ASCII character '\xf3' in file _redacted_ on line 81, but no encoding declared; see http://www.python.org/peps/pep-0263.html for details Once your program is working correctly, or, if you aren't using python's console or any other console to look at output, then you will probably really only care about #1 on the list. System default and console encoding are not that important unless you need to look at output and/or you are using the builtin unicode() function (without any encoding parameters) instead of the string.decode() function. I wrote a demo function I will paste into the bottom of this gigantic mess that I hope correctly demonstrates the items in my list. Here is some of the output when I run the character 'ó' through the demo function, showing how various methods react to the character as input. My system encoding and console output are both set to utf_8 for this run: '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Now I will change the system and console encoding to latin_1, and I get this output for the same input: 'ó' = original char <type 'str'> repr(char)='\xf3' 'ó' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' 'ó' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Notice that the 'original' character displays correctly and the builtin unicode() function works now. Now I change my console output back to utf_8. '?' = original char <type 'str'> repr(char)='\xf3' '?' = unicode(char) <type 'unicode'> repr(unicode(char))=u'\xf3' '?' = char.decode('latin_1') <type 'unicode'> repr(char.decode('latin_1'))=u'\xf3' '?' = char.decode('utf_8') ERROR: 'utf8' codec can't decode byte 0xf3 in position 0: unexpected end of data Here everything still works the same as last time but the console can't display the output correctly. Etc. The function below also displays more information that this and hopefully would help someone figure out where the gap in their understanding is. I know all this information is in other places and more thoroughly dealt with there, but I hope that this would be a good kickoff point for someone trying to get coding with python and/or sqlite. Ideas are great but sometimes source code can save you a day or two of trying to figure out what functions do what. Disclaimers: I'm no encoding expert, I put this together to help my own understanding. I kept building on it when I should have probably started passing functions as arguments to avoid so much redundant code, so if I can I'll make it more concise. Also, utf_8 and latin_1 are by no means the only encoding schemes, they are just the two I was playing around with because I think they handle everything I need. Add your own encoding schemes to the demo function and test your own input. One more thing: there are apparently crazy application developers making life difficult in Windows. #!/usr/bin/env python # -*- coding: utf_8 -*- import os import sys def encodingDemo(str): validStrings = () try: print "str =",str,"{0} repr(str) = {1}".format(type(str), repr(str)) validStrings += ((str,""),) except UnicodeEncodeError as ude: print "Couldn't print the str itself because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print ude try: x = unicode(str) print "unicode(str) = ",x validStrings+= ((x, " decoded into unicode by the default system encoding"),) except UnicodeDecodeError as ude: print "ERROR. unicode(str) couldn't decode the string because the system encoding is set to an encoding that doesn't understand some character in the string." print "\tThe system encoding is set to {0}. See error:\n\t".format(sys.getdefaultencoding()), print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the unicode(str) because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('latin_1') print "str.decode('latin_1') =",x validStrings+= ((x, " decoded with latin_1 into unicode"),) try: print "str.decode('latin_1').encode('utf_8') =",str.decode('latin_1').encode('utf_8') validStrings+= ((x, " decoded with latin_1 into unicode and encoded into utf_8"),) except UnicodeDecodeError as ude: print "The string was decoded into unicode using the latin_1 encoding, but couldn't be encoded into utf_8. See error:\n\t", print ude except UnicodeDecodeError as ude: print "Something didn't work, probably because the string wasn't latin_1 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('latin_1') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t", print uee try: x = str.decode('utf_8') print "str.decode('utf_8') =",x validStrings+= ((x, " decoded with utf_8 into unicode"),) try: print "str.decode('utf_8').encode('latin_1') =",str.decode('utf_8').encode('latin_1') except UnicodeDecodeError as ude: print "str.decode('utf_8').encode('latin_1') didn't work. The string was decoded into unicode using the utf_8 encoding, but couldn't be encoded into latin_1. See error:\n\t", validStrings+= ((x, " decoded with utf_8 into unicode and encoded into latin_1"),) print ude except UnicodeDecodeError as ude: print "str.decode('utf_8') didn't work, probably because the string wasn't utf_8 encoded. See error:\n\t", print ude except UnicodeEncodeError as uee: print "ERROR. Couldn't print the str.decode('utf_8') because the console is set to an encoding that doesn't understand some character in the string. See error:\n\t",uee print print "Printing information about each character in the original string." for char in str: try: print "\t'" + char + "' = original char {0} repr(char)={1}".format(type(char), repr(char)) except UnicodeDecodeError as ude: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), ude) except UnicodeEncodeError as uee: print "\t'?' = original char {0} repr(char)={1} ERROR PRINTING: {2}".format(type(char), repr(char), uee) print uee try: x = unicode(char) print "\t'" + x + "' = unicode(char) {1} repr(unicode(char))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = unicode(char) ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = unicode(char) {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('latin_1') print "\t'" + x + "' = char.decode('latin_1') {1} repr(char.decode('latin_1'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('latin_1') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('latin_1') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) try: x = char.decode('utf_8') print "\t'" + x + "' = char.decode('utf_8') {1} repr(char.decode('utf_8'))={2}".format(x, type(x), repr(x)) except UnicodeDecodeError as ude: print "\t'?' = char.decode('utf_8') ERROR: {0}".format(ude) except UnicodeEncodeError as uee: print "\t'?' = char.decode('utf_8') {0} repr(char)={1} ERROR PRINTING: {2}".format(type(x), repr(x), uee) print x = 'ó' encodingDemo(x) Much thanks for the answers below and especially to @John Machin for answering so thoroughly.

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• Problems extracting information from RSS feed description field

  - by Graeme

  Hi, I've built an iPhone application using the parsing code from the TopSongs sample iPhone application. I've hit a problem though - the feed I'm trying to parse data from doesn't have a separate field for every piece of information (i.e. if it was for a feed about dogs, all the information such as dog type, dog age and dog price is contained in the feed. However, the TopSongs app relies on information having its own tags, so instead of using it uses and . So my question is this. How do I extract this information from the description field so that it can be parsed using the TopSongs parser? Can you somehow extract the dog age, price and type information using Yahoo Pipes and use that RSS feed for the feed? Or is there code that I can add to do it in application? Update: To view the code of my application parser (based on the TopSongs Core Data Apple provided application, see below. Here's a sample of one item from the the actual RSS feed I'm using (the description is longer, and has status,size, and a couple of other fields, but they're all formatted the same.: <item> <title>MOE, MARGRET STREET</title> <description> <b>District/Region:</b>&nbsp;REGION 09</br><b>Location:</b>&nbsp;MOE</br><b>Name:</b>&nbsp;MARGRET STREET</br></description> <pubDate>Thu,11 Mar 2010 05:43:03 GMT</pubDate> <guid>1266148</guid> </item> /* File: iTunesRSSImporter.m Abstract: Downloads, parses, and imports the iTunes top songs RSS feed into Core Data. Version: 1.1 Disclaimer: IMPORTANT: This Apple software is supplied to you by Apple Inc. ("Apple") in consideration of your agreement to the following terms, and your use, installation, modification or redistribution of this Apple software constitutes acceptance of these terms. If you do not agree with these terms, please do not use, install, modify or redistribute this Apple software. In consideration of your agreement to abide by the following terms, and subject to these terms, Apple grants you a personal, non-exclusive license, under Apple's copyrights in this original Apple software (the "Apple Software"), to use, reproduce, modify and redistribute the Apple Software, with or without modifications, in source and/or binary forms; provided that if you redistribute the Apple Software in its entirety and without modifications, you must retain this notice and the following text and disclaimers in all such redistributions of the Apple Software. Neither the name, trademarks, service marks or logos of Apple Inc. may be used to endorse or promote products derived from the Apple Software without specific prior written permission from Apple. Except as expressly stated in this notice, no other rights or licenses, express or implied, are granted by Apple herein, including but not limited to any patent rights that may be infringed by your derivative works or by other works in which the Apple Software may be incorporated. The Apple Software is provided by Apple on an "AS IS" basis. APPLE MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS. IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Copyright (C) 2009 Apple Inc. All Rights Reserved. */ #import "iTunesRSSImporter.h" #import "Song.h" #import "Category.h" #import "CategoryCache.h" #import <libxml/tree.h> // Function prototypes for SAX callbacks. This sample implements a minimal subset of SAX callbacks. // Depending on your application's needs, you might want to implement more callbacks. static void startElementSAX(void *context, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI, int nb_namespaces, const xmlChar **namespaces, int nb_attributes, int nb_defaulted, const xmlChar **attributes); static void endElementSAX(void *context, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI); static void charactersFoundSAX(void *context, const xmlChar *characters, int length); static void errorEncounteredSAX(void *context, const char *errorMessage, ...); // Forward reference. The structure is defined in full at the end of the file. static xmlSAXHandler simpleSAXHandlerStruct; // Class extension for private properties and methods. @interface iTunesRSSImporter () @property BOOL storingCharacters; @property (nonatomic, retain) NSMutableData *characterBuffer; @property BOOL done; @property BOOL parsingASong; @property NSUInteger countForCurrentBatch; @property (nonatomic, retain) Song *currentSong; @property (nonatomic, retain) NSURLConnection *rssConnection; @property (nonatomic, retain) NSDateFormatter *dateFormatter; // The autorelease pool property is assign because autorelease pools cannot be retained. @property (nonatomic, assign) NSAutoreleasePool *importPool; @end static double lookuptime = 0; @implementation iTunesRSSImporter @synthesize iTunesURL, delegate, persistentStoreCoordinator; @synthesize rssConnection, done, parsingASong, storingCharacters, currentSong, countForCurrentBatch, characterBuffer, dateFormatter, importPool; - (void)dealloc { [iTunesURL release]; [characterBuffer release]; [currentSong release]; [rssConnection release]; [dateFormatter release]; [persistentStoreCoordinator release]; [insertionContext release]; [songEntityDescription release]; [theCache release]; [super dealloc]; } - (void)main { self.importPool = [[NSAutoreleasePool alloc] init]; if (delegate && [delegate respondsToSelector:@selector(importerDidSave:)]) { [[NSNotificationCenter defaultCenter] addObserver:delegate selector:@selector(importerDidSave:) name:NSManagedObjectContextDidSaveNotification object:self.insertionContext]; } done = NO; self.dateFormatter = [[[NSDateFormatter alloc] init] autorelease]; [dateFormatter setDateStyle:NSDateFormatterLongStyle]; [dateFormatter setTimeStyle:NSDateFormatterNoStyle]; // necessary because iTunes RSS feed is not localized, so if the device region has been set to other than US // the date formatter must be set to US locale in order to parse the dates [dateFormatter setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:@"US"] autorelease]]; self.characterBuffer = [NSMutableData data]; NSURLRequest *theRequest = [NSURLRequest requestWithURL:iTunesURL]; // create the connection with the request and start loading the data rssConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; // This creates a context for "push" parsing in which chunks of data that are not "well balanced" can be passed // to the context for streaming parsing. The handler structure defined above will be used for all the parsing. // The second argument, self, will be passed as user data to each of the SAX handlers. The last three arguments // are left blank to avoid creating a tree in memory. context = xmlCreatePushParserCtxt(&simpleSAXHandlerStruct, self, NULL, 0, NULL); if (rssConnection != nil) { do { [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; } while (!done); } // Display the total time spent finding a specific object for a relationship NSLog(@"lookup time %f", lookuptime); // Release resources used only in this thread. xmlFreeParserCtxt(context); self.characterBuffer = nil; self.dateFormatter = nil; self.rssConnection = nil; self.currentSong = nil; [theCache release]; theCache = nil; NSError *saveError = nil; NSAssert1([insertionContext save:&saveError], @"Unhandled error saving managed object context in import thread: %@", [saveError localizedDescription]); if (delegate && [delegate respondsToSelector:@selector(importerDidSave:)]) { [[NSNotificationCenter defaultCenter] removeObserver:delegate name:NSManagedObjectContextDidSaveNotification object:self.insertionContext]; } if (self.delegate != nil && [self.delegate respondsToSelector:@selector(importerDidFinishParsingData:)]) { [self.delegate importerDidFinishParsingData:self]; } [importPool release]; self.importPool = nil; } - (NSManagedObjectContext *)insertionContext { if (insertionContext == nil) { insertionContext = [[NSManagedObjectContext alloc] init]; [insertionContext setPersistentStoreCoordinator:self.persistentStoreCoordinator]; } return insertionContext; } - (void)forwardError:(NSError *)error { if (self.delegate != nil && [self.delegate respondsToSelector:@selector(importer:didFailWithError:)]) { [self.delegate importer:self didFailWithError:error]; } } - (NSEntityDescription *)songEntityDescription { if (songEntityDescription == nil) { songEntityDescription = [[NSEntityDescription entityForName:@"Song" inManagedObjectContext:self.insertionContext] retain]; } return songEntityDescription; } - (CategoryCache *)theCache { if (theCache == nil) { theCache = [[CategoryCache alloc] init]; theCache.managedObjectContext = self.insertionContext; } return theCache; } - (Song *)currentSong { if (currentSong == nil) { currentSong = [[Song alloc] initWithEntity:self.songEntityDescription insertIntoManagedObjectContext:self.insertionContext]; } return currentSong; } #pragma mark NSURLConnection Delegate methods // Forward errors to the delegate. - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { [self performSelectorOnMainThread:@selector(forwardError:) withObject:error waitUntilDone:NO]; // Set the condition which ends the run loop. done = YES; } // Called when a chunk of data has been downloaded. - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { // Process the downloaded chunk of data. xmlParseChunk(context, (const char *)[data bytes], [data length], 0); } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { // Signal the context that parsing is complete by passing "1" as the last parameter. xmlParseChunk(context, NULL, 0, 1); context = NULL; // Set the condition which ends the run loop. done = YES; } #pragma mark Parsing support methods static const NSUInteger kImportBatchSize = 20; - (void)finishedCurrentSong { parsingASong = NO; self.currentSong = nil; countForCurrentBatch++; // Periodically purge the autorelease pool and save the context. The frequency of this action may need to be tuned according to the // size of the objects being parsed. The goal is to keep the autorelease pool from growing too large, but // taking this action too frequently would be wasteful and reduce performance. if (countForCurrentBatch == kImportBatchSize) { [importPool release]; self.importPool = [[NSAutoreleasePool alloc] init]; NSError *saveError = nil; NSAssert1([insertionContext save:&saveError], @"Unhandled error saving managed object context in import thread: %@", [saveError localizedDescription]); countForCurrentBatch = 0; } } /* Character data is appended to a buffer until the current element ends. */ - (void)appendCharacters:(const char *)charactersFound length:(NSInteger)length { [characterBuffer appendBytes:charactersFound length:length]; } - (NSString *)currentString { // Create a string with the character data using UTF-8 encoding. UTF-8 is the default XML data encoding. NSString *currentString = [[[NSString alloc] initWithData:characterBuffer encoding:NSUTF8StringEncoding] autorelease]; [characterBuffer setLength:0]; return currentString; } @end #pragma mark SAX Parsing Callbacks // The following constants are the XML element names and their string lengths for parsing comparison. // The lengths include the null terminator, to ensure exact matches. static const char *kName_Item = "item"; static const NSUInteger kLength_Item = 5; static const char *kName_Title = "title"; static const NSUInteger kLength_Title = 6; static const char *kName_Category = "category"; static const NSUInteger kLength_Category = 9; static const char *kName_Itms = "itms"; static const NSUInteger kLength_Itms = 5; static const char *kName_Artist = "description"; static const NSUInteger kLength_Artist = 7; static const char *kName_Album = "description"; static const NSUInteger kLength_Album = 6; static const char *kName_ReleaseDate = "releasedate"; static const NSUInteger kLength_ReleaseDate = 12; /* This callback is invoked when the importer finds the beginning of a node in the XML. For this application, out parsing needs are relatively modest - we need only match the node name. An "item" node is a record of data about a song. In that case we create a new Song object. The other nodes of interest are several of the child nodes of the Song currently being parsed. For those nodes we want to accumulate the character data in a buffer. Some of the child nodes use a namespace prefix. */ static void startElementSAX(void *parsingContext, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI, int nb_namespaces, const xmlChar **namespaces, int nb_attributes, int nb_defaulted, const xmlChar **attributes) { iTunesRSSImporter *importer = (iTunesRSSImporter *)parsingContext; // The second parameter to strncmp is the name of the element, which we known from the XML schema of the feed. // The third parameter to strncmp is the number of characters in the element name, plus 1 for the null terminator. if (prefix == NULL && !strncmp((const char *)localname, kName_Item, kLength_Item)) { importer.parsingASong = YES; } else if (importer.parsingASong && ( (prefix == NULL && (!strncmp((const char *)localname, kName_Title, kLength_Title) || !strncmp((const char *)localname, kName_Category, kLength_Category))) || ((prefix != NULL && !strncmp((const char *)prefix, kName_Itms, kLength_Itms)) && (!strncmp((const char *)localname, kName_Artist, kLength_Artist) || !strncmp((const char *)localname, kName_Album, kLength_Album) || !strncmp((const char *)localname, kName_ReleaseDate, kLength_ReleaseDate))) )) { importer.storingCharacters = YES; } } /* This callback is invoked when the parse reaches the end of a node. At that point we finish processing that node, if it is of interest to us. For "item" nodes, that means we have completed parsing a Song object. We pass the song to a method in the superclass which will eventually deliver it to the delegate. For the other nodes we care about, this means we have all the character data. The next step is to create an NSString using the buffer contents and store that with the current Song object. */ static void endElementSAX(void *parsingContext, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI) { iTunesRSSImporter *importer = (iTunesRSSImporter *)parsingContext; if (importer.parsingASong == NO) return; if (prefix == NULL) { if (!strncmp((const char *)localname, kName_Item, kLength_Item)) { [importer finishedCurrentSong]; } else if (!strncmp((const char *)localname, kName_Title, kLength_Title)) { importer.currentSong.title = importer.currentString; } else if (!strncmp((const char *)localname, kName_Category, kLength_Category)) { double before = [NSDate timeIntervalSinceReferenceDate]; Category *category = [importer.theCache categoryWithName:importer.currentString]; double delta = [NSDate timeIntervalSinceReferenceDate] - before; lookuptime += delta; importer.currentSong.category = category; } } else if (!strncmp((const char *)prefix, kName_Itms, kLength_Itms)) { if (!strncmp((const char *)localname, kName_Artist, kLength_Artist)) { NSString *string = importer.currentSong.artist; NSArray *strings = [string componentsSeparatedByString: @", "]; //importer.currentSong.artist = importer.currentString; } else if (!strncmp((const char *)localname, kName_Album, kLength_Album)) { importer.currentSong.album = importer.currentString; } else if (!strncmp((const char *)localname, kName_ReleaseDate, kLength_ReleaseDate)) { NSString *dateString = importer.currentString; importer.currentSong.releaseDate = [importer.dateFormatter dateFromString:dateString]; } } importer.storingCharacters = NO; } /* This callback is invoked when the parser encounters character data inside a node. The importer class determines how to use the character data. */ static void charactersFoundSAX(void *parsingContext, const xmlChar *characterArray, int numberOfCharacters) { iTunesRSSImporter *importer = (iTunesRSSImporter *)parsingContext; // A state variable, "storingCharacters", is set when nodes of interest begin and end. // This determines whether character data is handled or ignored. if (importer.storingCharacters == NO) return; [importer appendCharacters:(const char *)characterArray length:numberOfCharacters]; } /* A production application should include robust error handling as part of its parsing implementation. The specifics of how errors are handled depends on the application. */ static void errorEncounteredSAX(void *parsingContext, const char *errorMessage, ...) { // Handle errors as appropriate for your application. NSCAssert(NO, @"Unhandled error encountered during SAX parse."); } // The handler struct has positions for a large number of callback functions. If NULL is supplied at a given position, // that callback functionality won't be used. Refer to libxml documentation at http://www.xmlsoft.org for more information // about the SAX callbacks. static xmlSAXHandler simpleSAXHandlerStruct = { NULL, /* internalSubset */ NULL, /* isStandalone */ NULL, /* hasInternalSubset */ NULL, /* hasExternalSubset */ NULL, /* resolveEntity */ NULL, /* getEntity */ NULL, /* entityDecl */ NULL, /* notationDecl */ NULL, /* attributeDecl */ NULL, /* elementDecl */ NULL, /* unparsedEntityDecl */ NULL, /* setDocumentLocator */ NULL, /* startDocument */ NULL, /* endDocument */ NULL, /* startElement*/ NULL, /* endElement */ NULL, /* reference */ charactersFoundSAX, /* characters */ NULL, /* ignorableWhitespace */ NULL, /* processingInstruction */ NULL, /* comment */ NULL, /* warning */ errorEncounteredSAX, /* error */ NULL, /* fatalError //: unused error() get all the errors */ NULL, /* getParameterEntity */ NULL, /* cdataBlock */ NULL, /* externalSubset */ XML_SAX2_MAGIC, // NULL, startElementSAX, /* startElementNs */ endElementSAX, /* endElementNs */ NULL, /* serror */ }; Thanks.

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• Red Gate Coder interviews: Alex Davies

  - by Michael Williamson

  Alex Davies has been a software engineer at Red Gate since graduating from university, and is currently busy working on .NET Demon. We talked about tackling parallel programming with his actors framework, a scientific approach to debugging, and how JavaScript is going to affect the programming languages we use in years to come. So, if we start at the start, how did you get started in programming? When I was seven or eight, I was given a BBC Micro for Christmas. I had asked for a Game Boy, but my dad thought it would be better to give me a proper computer. For a year or so, I only played games on it, but then I found the user guide for writing programs in it. I gradually started doing more stuff on it and found it fun. I liked creating. As I went into senior school I continued to write stuff on there, trying to write games that weren’t very good. I got a real computer when I was fourteen and found ways to write BASIC on it. Visual Basic to start with, and then something more interesting than that. How did you learn to program? Was there someone helping you out? Absolutely not! I learnt out of a book, or by experimenting. I remember the first time I found a loop, I was like “Oh my God! I don’t have to write out the same line over and over and over again any more. It’s amazing!” When did you think this might be something that you actually wanted to do as a career? For a long time, I thought it wasn’t something that you would do as a career, because it was too much fun to be a career. I thought I’d do chemistry at university and some kind of career based on chemical engineering. And then I went to a careers fair at school when I was seventeen or eighteen, and it just didn’t interest me whatsoever. I thought “I could be a programmer, and there’s loads of money there, and I’m good at it, and it’s fun”, but also that I shouldn’t spoil my hobby. Now I don’t really program in my spare time any more, which is a bit of a shame, but I program all the rest of the time, so I can live with it. Do you think you learnt much about programming at university? Yes, definitely! I went into university knowing how to make computers do anything I wanted them to do. However, I didn’t have the language to talk about algorithms, so the algorithms course in my first year was massively important. Learning other language paradigms like functional programming was really good for breadth of understanding. Functional programming influences normal programming through design rather than actually using it all the time. I draw inspiration from it to write imperative programs which I think is actually becoming really fashionable now, but I’ve been doing it for ages. I did it first! There were also some courses on really odd programming languages, a bit of Prolog, a little bit of C. Having a little bit of each of those is something that I would have never done on my own, so it was important. And then there are knowledge-based courses which are about not programming itself but things that have been programmed like TCP. Those are really important for examples for how to approach things. Did you do any internships while you were at university? Yeah, I spent both of my summers at the same company. I thought I could code well before I went there. Looking back at the crap that I produced, it was only surpassed in its crappiness by all of the other code already in that company. I’m so much better at writing nice code now than I used to be back then. Was there just not a culture of looking after your code? There was, they just didn’t hire people for their abilities in that area. They hired people for raw IQ. The first indicator of it going wrong was that they didn’t have any computer scientists, which is a bit odd in a programming company. But even beyond that they didn’t have people who learnt architecture from anyone else. Most of them had started straight out of university, so never really had experience or mentors to learn from. There wasn’t the experience to draw from to teach each other. In the second half of my second internship, I was being given tasks like looking at new technologies and teaching people stuff. Interns shouldn’t be teaching people how to do their jobs! All interns are going to have little nuggets of things that you don’t know about, but they shouldn’t consistently be the ones who know the most. It’s not a good environment to learn. I was going to ask how you found working with people who were more experienced than you… When I reached Red Gate, I found some people who were more experienced programmers than me, and that was difficult. I’ve been coding since I was tiny. At university there were people who were cleverer than me, but there weren’t very many who were more experienced programmers than me. During my internship, I didn’t find anyone who I classed as being a noticeably more experienced programmer than me. So, it was a shock to the system to have valid criticisms rather than just formatting criticisms. However, Red Gate’s not so big on the actual code review, at least it wasn’t when I started. We did an entire product release and then somebody looked over all of the UI of that product which I’d written and say what they didn’t like. By that point, it was way too late and I’d disagree with them. Do you think the lack of code reviews was a bad thing? I think if there’s going to be any oversight of new people, then it should be continuous rather than chunky. For me I don’t mind too much, I could go out and get oversight if I wanted it, and in those situations I felt comfortable without it. If I was managing the new person, then maybe I’d be keener on oversight and then the right way to do it is continuously and in very, very small chunks. Have you had any significant projects you’ve worked on outside of a job? When I was a teenager I wrote all sorts of stuff. I used to write games, I derived how to do isomorphic projections myself once. I didn’t know what the word was so I couldn’t Google for it, so I worked it out myself. It was horrifically complicated. But it sort of tailed off when I started at university, and is now basically zero. If I do side-projects now, they tend to be work-related side projects like my actors framework, NAct, which I started in a down tools week. Could you explain a little more about NAct? It is a little C# framework for writing parallel code more easily. Parallel programming is difficult when you need to write to shared data. Sometimes parallel programming is easy because you don’t need to write to shared data. When you do need to access shared data, you could just have your threads pile in and do their work, but then you would screw up the data because the threads would trample on each other’s toes. You could lock, but locks are really dangerous if you’re using more than one of them. You get interactions like deadlocks, and that’s just nasty. Actors instead allows you to say this piece of data belongs to this thread of execution, and nobody else can read it. If you want to read it, then ask that thread of execution for a piece of it by sending a message, and it will send the data back by a message. And that avoids deadlocks as long as you follow some obvious rules about not making your actors sit around waiting for other actors to do something. There are lots of ways to write actors, NAct allows you to do it as if it was method calls on other objects, which means you get all the strong type-safety that C# programmers like. Do you think that this is suitable for the majority of parallel programming, or do you think it’s only suitable for specific cases? It’s suitable for most difficult parallel programming. If you’ve just got a hundred web requests which are all independent of each other, then I wouldn’t bother because it’s easier to just spin them up in separate threads and they can proceed independently of each other. But where you’ve got difficult parallel programming, where you’ve got multiple threads accessing multiple bits of data in multiple ways at different times, then actors is at least as good as all other ways, and is, I reckon, easier to think about. When you’re using actors, you presumably still have to write your code in a different way from you would otherwise using single-threaded code. You can’t use actors with any methods that have return types, because you’re not allowed to call into another actor and wait for it. If you want to get a piece of data out of another actor, then you’ve got to use tasks so that you can use “async” and “await” to await asynchronously for it. But other than that, you can still stick things in classes so it’s not too different really. Rather than having thousands of objects with mutable state, you can use component-orientated design, where there are only a few mutable classes which each have a small number of instances. Then there can be thousands of immutable objects. If you tend to do that anyway, then actors isn’t much of a jump. If I’ve already built my system without any parallelism, how hard is it to add actors to exploit all eight cores on my desktop? Usually pretty easy. If you can identify even one boundary where things look like messages and you have components where some objects live on one side and these other objects live on the other side, then you can have a granddaddy object on one side be an actor and it will parallelise as it goes across that boundary. Not too difficult. If we do get 1000-core desktop PCs, do you think actors will scale up? It’s hard. There are always in the order of twenty to fifty actors in my whole program because I tend to write each component as actors, and I tend to have one instance of each component. So this won’t scale to a thousand cores. What you can do is write data structures out of actors. I use dictionaries all over the place, and if you need a dictionary that is going to be accessed concurrently, then you could build one of those out of actors in no time. You can use queuing to marshal requests between different slices of the dictionary which are living on different threads. So it’s like a distributed hash table but all of the chunks of it are on the same machine. That means that each of these thousand processors has cached one small piece of the dictionary. I reckon it wouldn’t be too big a leap to start doing proper parallelism. Do you think it helps if actors get baked into the language, similarly to Erlang? Erlang is excellent in that it has thread-local garbage collection. C# doesn’t, so there’s a limit to how well C# actors can possibly scale because there’s a single garbage collected heap shared between all of them. When you do a global garbage collection, you’ve got to stop all of the actors, which is seriously expensive, whereas in Erlang garbage collections happen per-actor, so they’re insanely cheap. However, Erlang deviated from all the sensible language design that people have used recently and has just come up with crazy stuff. You can definitely retrofit thread-local garbage collection to .NET, and then it’s quite well-suited to support actors, even if it’s not baked into the language. Speaking of language design, do you have a favourite programming language? I’ll choose a language which I’ve never written before. I like the idea of Scala. It sounds like C#, only with some of the niggles gone. I enjoy writing static types. It means you don’t have to writing tests so much. When you say it doesn’t have some of the niggles? C# doesn’t allow the use of a property as a method group. It doesn’t have Scala case classes, or sum types, where you can do a switch statement and the compiler checks that you’ve checked all the cases, which is really useful in functional-style programming. Pattern-matching, in other words. That’s actually the major niggle. C# is pretty good, and I’m quite happy with C#. And what about going even further with the type system to remove the need for tests to something like Haskell? Or is that a step too far? I’m quite a pragmatist, I don’t think I could deal with trying to write big systems in languages with too few other users, especially when learning how to structure things. I just don’t know anyone who can teach me, and the Internet won’t teach me. That’s the main reason I wouldn’t use it. If I turned up at a company that writes big systems in Haskell, I would have no objection to that, but I wouldn’t instigate it. What about things in C#? For instance, there’s contracts in C#, so you can try to statically verify a bit more about your code. Do you think that’s useful, or just not worthwhile? I’ve not really tried it. My hunch is that it needs to be built into the language and be quite mathematical for it to work in real life, and that doesn’t seem to have ended up true for C# contracts. I don’t think anyone who’s tried them thinks they’re any good. I might be wrong. On a slightly different note, how do you like to debug code? I think I’m quite an odd debugger. I use guesswork extremely rarely, especially if something seems quite difficult to debug. I’ve been bitten spending hours and hours on guesswork and not being scientific about debugging in the past, so now I’m scientific to a fault. What I want is to see the bug happening in the debugger, to step through the bug happening. To watch the program going from a valid state to an invalid state. When there’s a bug and I can’t work out why it’s happening, I try to find some piece of evidence which places the bug in one section of the code. From that experiment, I binary chop on the possible causes of the bug. I suppose that means binary chopping on places in the code, or binary chopping on a stage through a processing cycle. Basically, I’m very stupid about how I debug. I won’t make any guesses, I won’t use any intuition, I will only identify the experiment that’s going to binary chop most effectively and repeat rather than trying to guess anything. I suppose it’s quite top-down. Is most of the time then spent in the debugger? Absolutely, if at all possible I will never debug using print statements or logs. I don’t really hold much stock in outputting logs. If there’s any bug which can be reproduced locally, I’d rather do it in the debugger than outputting logs. And with SmartAssembly error reporting, there’s not a lot that can’t be either observed in an error report and just fixed, or reproduced locally. And in those other situations, maybe I’ll use logs. But I hate using logs. You stare at the log, trying to guess what’s going on, and that’s exactly what I don’t like doing. You have to just look at it and see does this look right or wrong. We’ve covered how you get to grip with bugs. How do you get to grips with an entire codebase? I watch it in the debugger. I find little bugs and then try to fix them, and mostly do it by watching them in the debugger and gradually getting an understanding of how the code works using my process of binary chopping. I have to do a lot of reading and watching code to choose where my slicing-in-half experiment is going to be. The last time I did it was SmartAssembly. The old code was a complete mess, but at least it did things top to bottom. There wasn’t too much of some of the big abstractions where flow of control goes all over the place, into a base class and back again. Code’s really hard to understand when that happens. So I like to choose a little bug and try to fix it, and choose a bigger bug and try to fix it. Definitely learn by doing. I want to always have an aim so that I get a little achievement after every few hours of debugging. Once I’ve learnt the codebase I might be able to fix all the bugs in an hour, but I’d rather be using them as an aim while I’m learning the codebase. If I was a maintainer of a codebase, what should I do to make it as easy as possible for you to understand? Keep distinct concepts in different places. And name your stuff so that it’s obvious which concepts live there. You shouldn’t have some variable that gets set miles up the top of somewhere, and then is read miles down to choose some later behaviour. I’m talking from a very much SmartAssembly point of view because the old SmartAssembly codebase had tons and tons of these things, where it would read some property of the code and then deal with it later. Just thousands of variables in scope. Loads of things to think about. If you can keep concepts separate, then it aids me in my process of fixing bugs one at a time, because each bug is going to more or less be understandable in the one place where it is. And what about tests? Do you think they help at all? I’ve never had the opportunity to learn a codebase which has had tests, I don’t know what it’s like! What about when you’re actually developing? How useful do you find tests in finding bugs or regressions? Finding regressions, absolutely. Running bits of code that would be quite hard to run otherwise, definitely. It doesn’t happen very often that a test finds a bug in the first place. I don’t really buy nebulous promises like tests being a good way to think about the spec of the code. My thinking goes something like “This code works at the moment, great, ship it! Ah, there’s a way that this code doesn’t work. Okay, write a test, demonstrate that it doesn’t work, fix it, use the test to demonstrate that it’s now fixed, and keep the test for future regressions.” The most valuable tests are for bugs that have actually happened at some point, because bugs that have actually happened at some point, despite the fact that you think you’ve fixed them, are way more likely to appear again than new bugs are. Does that mean that when you write your code the first time, there are no tests? Often. The chance of there being a bug in a new feature is relatively unaffected by whether I’ve written a test for that new feature because I’m not good enough at writing tests to think of bugs that I would have written into the code. So not writing regression tests for all of your code hasn’t affected you too badly? There are different kinds of features. Some of them just always work, and are just not flaky, they just continue working whatever you throw at them. Maybe because the type-checker is particularly effective around them. Writing tests for those features which just tend to always work is a waste of time. And because it’s a waste of time I’ll tend to wait until a feature has demonstrated its flakiness by having bugs in it before I start trying to test it. You can get a feel for whether it’s going to be flaky code as you’re writing it. I try to write it to make it not flaky, but there are some things that are just inherently flaky. And very occasionally, I’ll think “this is going to be flaky” as I’m writing, and then maybe do a test, but not most of the time. How do you think your programming style has changed over time? I’ve got clearer about what the right way of doing things is. I used to flip-flop a lot between different ideas. Five years ago I came up with some really good ideas and some really terrible ideas. All of them seemed great when I thought of them, but they were quite diverse ideas, whereas now I have a smaller set of reliable ideas that are actually good for structuring code. So my code is probably more similar to itself than it used to be back in the day, when I was trying stuff out. I’ve got more disciplined about encapsulation, I think. There are operational things like I use actors more now than I used to, and that forces me to use immutability more than I used to. The first code that I wrote in Red Gate was the memory profiler UI, and that was an actor, I just didn’t know the name of it at the time. I don’t really use object-orientation. By object-orientation, I mean having n objects of the same type which are mutable. I want a constant number of objects that are mutable, and they should be different types. I stick stuff in dictionaries and then have one thing that owns the dictionary and puts stuff in and out of it. That’s definitely a pattern that I’ve seen recently. I think maybe I’m doing functional programming. Possibly. It’s plausible. If you had to summarise the essence of programming in a pithy sentence, how would you do it? Programming is the form of art that, without losing any of the beauty of architecture or fine art, allows you to produce things that people love and you make money from. So you think it’s an art rather than a science? It’s a little bit of engineering, a smidgeon of maths, but it’s not science. Like architecture, programming is on that boundary between art and engineering. If you want to do it really nicely, it’s mostly art. You can get away with doing architecture and programming entirely by having a good engineering mind, but you’re not going to produce anything nice. You’re not going to have joy doing it if you’re an engineering mind. Architects who are just engineering minds are not going to enjoy their job. I suppose engineering is the foundation on which you build the art. Exactly. How do you think programming is going to change over the next ten years? There will be an unfortunate shift towards dynamically-typed languages, because of JavaScript. JavaScript has an unfair advantage. JavaScript’s unfair advantage will cause more people to be exposed to dynamically-typed languages, which means other dynamically-typed languages crop up and the best features go into dynamically-typed languages. Then people conflate the good features with the fact that it’s dynamically-typed, and more investment goes into dynamically-typed languages. They end up better, so people use them. What about the idea of compiling other languages, possibly statically-typed, to JavaScript? It’s a reasonable idea. I would like to do it, but I don’t think enough people in the world are going to do it to make it pick up. The hordes of beginners are the lifeblood of a language community. They are what makes there be good tools and what makes there be vibrant community websites. And any particular thing which is the same as JavaScript only with extra stuff added to it, although it might be technically great, is not going to have the hordes of beginners. JavaScript is always to be quickest and easiest way for a beginner to start programming in the browser. And dynamically-typed languages are great for beginners. Compilers are pretty scary and beginners don’t write big code. And having your errors come up in the same place, whether they’re statically checkable errors or not, is quite nice for a beginner. If someone asked me to teach them some programming, I’d teach them JavaScript. If dynamically-typed languages are great for beginners, when do you think the benefits of static typing start to kick in? The value of having a statically typed program is in the tools that rely on the static types to produce a smooth IDE experience rather than actually telling me my compile errors. And only once you’re experienced enough a programmer that having a really smooth IDE experience makes a blind bit of difference, does static typing make a blind bit of difference. So it’s not really about size of codebase. If I go and write up a tiny program, I’m still going to get value out of writing it in C# using ReSharper because I’m experienced with C# and ReSharper enough to be able to write code five times faster if I have that help. Any other visions of the future? Nobody’s going to use actors. Because everyone’s going to be running on single-core VMs connected over network-ready protocols like JSON over HTTP. So, parallelism within one operating system is going to die. But until then, you should use actors. More Red Gater Coder interviews

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• The Incremental Architect&rsquo;s Napkin - #5 - Design functions for extensibility and readability

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/08/24/the-incremental-architectrsquos-napkin---5---design-functions-for.aspx The functionality of programs is entered via Entry Points. So what we´re talking about when designing software is a bunch of functions handling the requests represented by and flowing in through those Entry Points. Designing software thus consists of at least three phases: Analyzing the requirements to find the Entry Points and their signatures Designing the functionality to be executed when those Entry Points get triggered Implementing the functionality according to the design aka coding I presume, you´re familiar with phase 1 in some way. And I guess you´re proficient in implementing functionality in some programming language. But in my experience developers in general are not experienced in going through an explicit phase 2. “Designing functionality? What´s that supposed to mean?” you might already have thought. Here´s my definition: To design functionality (or functional design for short) means thinking about… well, functions. You find a solution for what´s supposed to happen when an Entry Point gets triggered in terms of functions. A conceptual solution that is, because those functions only exist in your head (or on paper) during this phase. But you may have guess that, because it´s “design” not “coding”. And here is, what functional design is not: It´s not about logic. Logic is expressions (e.g. +, -, && etc.) and control statements (e.g. if, switch, for, while etc.). Also I consider calling external APIs as logic. It´s equally basic. It´s what code needs to do in order to deliver some functionality or quality. Logic is what´s doing that needs to be done by software. Transformations are either done through expressions or API-calls. And then there is alternative control flow depending on the result of some expression. Basically it´s just jumps in Assembler, sometimes to go forward (if, switch), sometimes to go backward (for, while, do). But calling your own function is not logic. It´s not necessary to produce any outcome. Functionality is not enhanced by adding functions (subroutine calls) to your code. Nor is quality increased by adding functions. No performance gain, no higher scalability etc. through functions. Functions are not relevant to functionality. Strange, isn´t it. What they are important for is security of investment. By introducing functions into our code we can become more productive (re-use) and can increase evolvability (higher unterstandability, easier to keep code consistent). That´s no small feat, however. Evolvable code can hardly be overestimated. That´s why to me functional design is so important. It´s at the core of software development. To sum this up: Functional design is on a level of abstraction above (!) logical design or algorithmic design. Functional design is only done until you get to a point where each function is so simple you are very confident you can easily code it. Functional design an logical design (which mostly is coding, but can also be done using pseudo code or flow charts) are complementary. Software needs both. If you start coding right away you end up in a tangled mess very quickly. Then you need back out through refactoring. Functional design on the other hand is bloodless without actual code. It´s just a theory with no experiments to prove it. But how to do functional design? An example of functional design Let´s assume a program to de-duplicate strings. The user enters a number of strings separated by commas, e.g. a, b, a, c, d, b, e, c, a. And the program is supposed to clear this list of all doubles, e.g. a, b, c, d, e. There is only one Entry Point to this program: the user triggers the de-duplication by starting the program with the string list on the command line C:\>deduplicate "a, b, a, c, d, b, e, c, a" a, b, c, d, e …or by clicking on a GUI button. This leads to the Entry Point function to get called. It´s the program´s main function in case of the batch version or a button click event handler in the GUI version. That´s the physical Entry Point so to speak. It´s inevitable. What then happens is a three step process: Transform the input data from the user into a request. Call the request handler. Transform the output of the request handler into a tangible result for the user. Or to phrase it a bit more generally: Accept input. Transform input into output. Present output. This does not mean any of these steps requires a lot of effort. Maybe it´s just one line of code to accomplish it. Nevertheless it´s a distinct step in doing the processing behind an Entry Point. Call it an aspect or a responsibility - and you will realize it most likely deserves a function of its own to satisfy the Single Responsibility Principle (SRP). Interestingly the above list of steps is already functional design. There is no logic, but nevertheless the solution is described - albeit on a higher level of abstraction than you might have done yourself. But it´s still on a meta-level. The application to the domain at hand is easy, though: Accept string list from command line De-duplicate Present de-duplicated strings on standard output And this concrete list of processing steps can easily be transformed into code:static void Main(string[] args) { var input = Accept_string_list(args); var output = Deduplicate(input); Present_deduplicated_string_list(output); } Instead of a big problem there are three much smaller problems now. If you think each of those is trivial to implement, then go for it. You can stop the functional design at this point. But maybe, just maybe, you´re not so sure how to go about with the de-duplication for example. Then just implement what´s easy right now, e.g.private static string Accept_string_list(string[] args) { return args[0]; } private static void Present_deduplicated_string_list( string[] output) { var line = string.Join(", ", output); Console.WriteLine(line); } Accept_string_list() contains logic in the form of an API-call. Present_deduplicated_string_list() contains logic in the form of an expression and an API-call. And then repeat the functional design for the remaining processing step. What´s left is the domain logic: de-duplicating a list of strings. How should that be done? Without any logic at our disposal during functional design you´re left with just functions. So which functions could make up the de-duplication? Here´s a suggestion: De-duplicate Parse the input string into a true list of strings. Register each string in a dictionary/map/set. That way duplicates get cast away. Transform the data structure into a list of unique strings. Processing step 2 obviously was the core of the solution. That´s where real creativity was needed. That´s the core of the domain. But now after this refinement the implementation of each step is easy again:private static string[] Parse_string_list(string input) { return input.Split(',') .Select(s => s.Trim()) .ToArray(); } private static Dictionary<string,object> Compile_unique_strings(string[] strings) { return strings.Aggregate( new Dictionary<string, object>(), (agg, s) => { agg[s] = null; return agg; }); } private static string[] Serialize_unique_strings( Dictionary<string,object> dict) { return dict.Keys.ToArray(); } With these three additional functions Main() now looks like this:static void Main(string[] args) { var input = Accept_string_list(args); var strings = Parse_string_list(input); var dict = Compile_unique_strings(strings); var output = Serialize_unique_strings(dict); Present_deduplicated_string_list(output); } I think that´s very understandable code: just read it from top to bottom and you know how the solution to the problem works. It´s a mirror image of the initial design: Accept string list from command line Parse the input string into a true list of strings. Register each string in a dictionary/map/set. That way duplicates get cast away. Transform the data structure into a list of unique strings. Present de-duplicated strings on standard output You can even re-generate the design by just looking at the code. Code and functional design thus are always in sync - if you follow some simple rules. But about that later. And as a bonus: all the functions making up the process are small - which means easy to understand, too. So much for an initial concrete example. Now it´s time for some theory. Because there is method to this madness ;-) The above has only scratched the surface. Introducing Flow Design Functional design starts with a given function, the Entry Point. Its goal is to describe the behavior of the program when the Entry Point is triggered using a process, not an algorithm. An algorithm consists of logic, a process on the other hand consists just of steps or stages. Each processing step transforms input into output or a side effect. Also it might access resources, e.g. a printer, a database, or just memory. Processing steps thus can rely on state of some sort. This is different from Functional Programming, where functions are supposed to not be stateful and not cause side effects.[1] In its simplest form a process can be written as a bullet point list of steps, e.g. Get data from user Output result to user Transform data Parse data Map result for output Such a compilation of steps - possibly on different levels of abstraction - often is the first artifact of functional design. It can be generated by a team in an initial design brainstorming. Next comes ordering the steps. What should happen first, what next etc.? Get data from user Parse data Transform data Map result for output Output result to user That´s great for a start into functional design. It´s better than starting to code right away on a given function using TDD. Please get me right: TDD is a valuable practice. But it can be unnecessarily hard if the scope of a functionn is too large. But how do you know beforehand without investing some thinking? And how to do this thinking in a systematic fashion? My recommendation: For any given function you´re supposed to implement first do a functional design. Then, once you´re confident you know the processing steps - which are pretty small - refine and code them using TDD. You´ll see that´s much, much easier - and leads to cleaner code right away. For more information on this approach I call “Informed TDD” read my book of the same title. Thinking before coding is smart. And writing down the solution as a bunch of functions possibly is the simplest thing you can do, I´d say. It´s more according to the KISS (Keep It Simple, Stupid) principle than returning constants or other trivial stuff TDD development often is started with. So far so good. A simple ordered list of processing steps will do to start with functional design. As shown in the above example such steps can easily be translated into functions. Moving from design to coding thus is simple. However, such a list does not scale. Processing is not always that simple to be captured in a list. And then the list is just text. Again. Like code. That means the design is lacking visuality. Textual representations need more parsing by your brain than visual representations. Plus they are limited in their “dimensionality”: text just has one dimension, it´s sequential. Alternatives and parallelism are hard to encode in text. In addition the functional design using numbered lists lacks data. It´s not visible what´s the input, output, and state of the processing steps. That´s why functional design should be done using a lightweight visual notation. No tool is necessary to draw such designs. Use pen and paper; a flipchart, a whiteboard, or even a napkin is sufficient. Visualizing processes The building block of the functional design notation is a functional unit. I mostly draw it like this: Something is done, it´s clear what goes in, it´s clear what comes out, and it´s clear what the processing step requires in terms of state or hardware. Whenever input flows into a functional unit it gets processed and output is produced and/or a side effect occurs. Flowing data is the driver of something happening. That´s why I call this approach to functional design Flow Design. It´s about data flow instead of control flow. Control flow like in algorithms is of no concern to functional design. Thinking about control flow simply is too low level. Once you start with control flow you easily get bogged down by tons of details. That´s what you want to avoid during design. Design is supposed to be quick, broad brush, abstract. It should give overview. But what about all the details? As Robert C. Martin rightly said: “Programming is abot detail”. Detail is a matter of code. Once you start coding the processing steps you designed you can worry about all the detail you want. Functional design does not eliminate all the nitty gritty. It just postpones tackling them. To me that´s also an example of the SRP. Function design has the responsibility to come up with a solution to a problem posed by a single function (Entry Point). And later coding has the responsibility to implement the solution down to the last detail (i.e. statement, API-call). TDD unfortunately mixes both responsibilities. It´s just coding - and thereby trying to find detailed implementations (green phase) plus getting the design right (refactoring). To me that´s one reason why TDD has failed to deliver on its promise for many developers. Using functional units as building blocks of functional design processes can be depicted very easily. Here´s the initial process for the example problem: For each processing step draw a functional unit and label it. Choose a verb or an “action phrase” as a label, not a noun. Functional design is about activities, not state or structure. Then make the output of an upstream step the input of a downstream step. Finally think about the data that should flow between the functional units. Write the data above the arrows connecting the functional units in the direction of the data flow. Enclose the data description in brackets. That way you can clearly see if all flows have already been specified. Empty brackets mean “no data is flowing”, but nevertheless a signal is sent. A name like “list” or “strings” in brackets describes the data content. Use lower case labels for that purpose. A name starting with an upper case letter like “String” or “Customer” on the other hand signifies a data type. If you like, you also can combine descriptions with data types by separating them with a colon, e.g. (list:string) or (strings:string[]). But these are just suggestions from my practice with Flow Design. You can do it differently, if you like. Just be sure to be consistent. Flows wired-up in this manner I call one-dimensional (1D). Each functional unit just has one input and/or one output. A functional unit without an output is possible. It´s like a black hole sucking up input without producing any output. Instead it produces side effects. A functional unit without an input, though, does make much sense. When should it start to work? What´s the trigger? That´s why in the above process even the first processing step has an input. If you like, view such 1D-flows as pipelines. Data is flowing through them from left to right. But as you can see, it´s not always the same data. It get´s transformed along its passage: (args) becomes a (list) which is turned into (strings). The Principle of Mutual Oblivion A very characteristic trait of flows put together from function units is: no functional units knows another one. They are all completely independent of each other. Functional units don´t know where their input is coming from (or even when it´s gonna arrive). They just specify a range of values they can process. And they promise a certain behavior upon input arriving. Also they don´t know where their output is going. They just produce it in their own time independent of other functional units. That means at least conceptually all functional units work in parallel. Functional units don´t know their “deployment context”. They now nothing about the overall flow they are place in. They are just consuming input from some upstream, and producing output for some downstream. That makes functional units very easy to test. At least as long as they don´t depend on state or resources. I call this the Principle of Mutual Oblivion (PoMO). Functional units are oblivious of others as well as an overall context/purpose. They are just parts of a whole focused on a single responsibility. How the whole is built, how a larger goal is achieved, is of no concern to the single functional units. By building software in such a manner, functional design interestingly follows nature. Nature´s building blocks for organisms also follow the PoMO. The cells forming your body do not know each other. Take a nerve cell “controlling” a muscle cell for example:[2] The nerve cell does not know anything about muscle cells, let alone the specific muscel cell it is “attached to”. Likewise the muscle cell does not know anything about nerve cells, let a lone a specific nerve cell “attached to” it. Saying “the nerve cell is controlling the muscle cell” thus only makes sense when viewing both from the outside. “Control” is a concept of the whole, not of its parts. Control is created by wiring-up parts in a certain way. Both cells are mutually oblivious. Both just follow a contract. One produces Acetylcholine (ACh) as output, the other consumes ACh as input. Where the ACh is going, where it´s coming from neither cell cares about. Million years of evolution have led to this kind of division of labor. And million years of evolution have produced organism designs (DNA) which lead to the production of these different cell types (and many others) and also to their co-location. The result: the overall behavior of an organism. How and why this happened in nature is a mystery. For our software, though, it´s clear: functional and quality requirements needs to be fulfilled. So we as developers have to become “intelligent designers” of “software cells” which we put together to form a “software organism” which responds in satisfying ways to triggers from it´s environment. My bet is: If nature gets complex organisms working by following the PoMO, who are we to not apply this recipe for success to our much simpler “machines”? So my rule is: Wherever there is functionality to be delivered, because there is a clear Entry Point into software, design the functionality like nature would do it. Build it from mutually oblivious functional units. That´s what Flow Design is about. In that way it´s even universal, I´d say. Its notation can also be applied to biology: Never mind labeling the functional units with nouns. That´s ok in Flow Design. You´ll do that occassionally for functional units on a higher level of abstraction or when their purpose is close to hardware. Getting a cockroach to roam your bedroom takes 1,000,000 nerve cells (neurons). Getting the de-duplication program to do its job just takes 5 “software cells” (functional units). Both, though, follow the same basic principle. Translating functional units into code Moving from functional design to code is no rocket science. In fact it´s straightforward. There are two simple rules: Translate an input port to a function. Translate an output port either to a return statement in that function or to a function pointer visible to that function. The simplest translation of a functional unit is a function. That´s what you saw in the above example. Functions are mutually oblivious. That why Functional Programming likes them so much. It makes them composable. Which is the reason, nature works according to the PoMO. Let´s be clear about one thing: There is no dependency injection in nature. For all of an organism´s complexity no DI container is used. Behavior is the result of smooth cooperation between mutually oblivious building blocks. Functions will often be the adequate translation for the functional units in your designs. But not always. Take for example the case, where a processing step should not always produce an output. Maybe the purpose is to filter input. Here the functional unit consumes words and produces words. But it does not pass along every word flowing in. Some words are swallowed. Think of a spell checker. It probably should not check acronyms for correctness. There are too many of them. Or words with no more than two letters. Such words are called “stop words”. In the above picture the optionality of the output is signified by the astrisk outside the brackets. It means: Any number of (word) data items can flow from the functional unit for each input data item. It might be none or one or even more. This I call a stream of data. Such behavior cannot be translated into a function where output is generated with return. Because a function always needs to return a value. So the output port is translated into a function pointer or continuation which gets passed to the subroutine when called:[3]void filter_stop_words( string word, Action<string> onNoStopWord) { if (...check if not a stop word...) onNoStopWord(word); } If you want to be nitpicky you might call such a function pointer parameter an injection. And technically you´re right. Conceptually, though, it´s not an injection. Because the subroutine is not functionally dependent on the continuation. Firstly continuations are procedures, i.e. subroutines without a return type. Remember: Flow Design is about unidirectional data flow. Secondly the name of the formal parameter is chosen in a way as to not assume anything about downstream processing steps. onNoStopWord describes a situation (or event) within the functional unit only. Translating output ports into function pointers helps keeping functional units mutually oblivious in cases where output is optional or produced asynchronically. Either pass the function pointer to the function upon call. Or make it global by putting it on the encompassing class. Then it´s called an event. In C# that´s even an explicit feature.class Filter { public void filter_stop_words( string word) { if (...check if not a stop word...) onNoStopWord(word); } public event Action<string> onNoStopWord; } When to use a continuation and when to use an event dependens on how a functional unit is used in flows and how it´s packed together with others into classes. You´ll see examples further down the Flow Design road. Another example of 1D functional design Let´s see Flow Design once more in action using the visual notation. How about the famous word wrap kata? Robert C. Martin has posted a much cited solution including an extensive reasoning behind his TDD approach. So maybe you want to compare it to Flow Design. The function signature given is:string WordWrap(string text, int maxLineLength) {...} That´s not an Entry Point since we don´t see an application with an environment and users. Nevertheless it´s a function which is supposed to provide a certain functionality. The text passed in has to be reformatted. The input is a single line of arbitrary length consisting of words separated by spaces. The output should consist of one or more lines of a maximum length specified. If a word is longer than a the maximum line length it can be split in multiple parts each fitting in a line. Flow Design Let´s start by brainstorming the process to accomplish the feat of reformatting the text. What´s needed? Words need to be assembled into lines Words need to be extracted from the input text The resulting lines need to be assembled into the output text Words too long to fit in a line need to be split Does sound about right? I guess so. And it shows a kind of priority. Long words are a special case. So maybe there is a hint for an incremental design here. First let´s tackle “average words” (words not longer than a line). Here´s the Flow Design for this increment: The the first three bullet points turned into functional units with explicit data added. As the signature requires a text is transformed into another text. See the input of the first functional unit and the output of the last functional unit. In between no text flows, but words and lines. That´s good to see because thereby the domain is clearly represented in the design. The requirements are talking about words and lines and here they are. But note the asterisk! It´s not outside the brackets but inside. That means it´s not a stream of words or lines, but lists or sequences. For each text a sequence of words is output. For each sequence of words a sequence of lines is produced. The asterisk is used to abstract from the concrete implementation. Like with streams. Whether the list of words gets implemented as an array or an IEnumerable is not important during design. It´s an implementation detail. Does any processing step require further refinement? I don´t think so. They all look pretty “atomic” to me. And if not… I can always backtrack and refine a process step using functional design later once I´ve gained more insight into a sub-problem. Implementation The implementation is straightforward as you can imagine. The processing steps can all be translated into functions. Each can be tested easily and separately. Each has a focused responsibility. And the process flow becomes just a sequence of function calls: Easy to understand. It clearly states how word wrapping works - on a high level of abstraction. And it´s easy to evolve as you´ll see. Flow Design - Increment 2 So far only texts consisting of “average words” are wrapped correctly. Words not fitting in a line will result in lines too long. Wrapping long words is a feature of the requested functionality. Whether it´s there or not makes a difference to the user. To quickly get feedback I decided to first implement a solution without this feature. But now it´s time to add it to deliver the full scope. Fortunately Flow Design automatically leads to code following the Open Closed Principle (OCP). It´s easy to extend it - instead of changing well tested code. How´s that possible? Flow Design allows for extension of functionality by inserting functional units into the flow. That way existing functional units need not be changed. The data flow arrow between functional units is a natural extension point. No need to resort to the Strategy Pattern. No need to think ahead where extions might need to be made in the future. I just “phase in” the remaining processing step: Since neither Extract words nor Reformat know of their environment neither needs to be touched due to the “detour”. The new processing step accepts the output of the existing upstream step and produces data compatible with the existing downstream step. Implementation - Increment 2 A trivial implementation checking the assumption if this works does not do anything to split long words. The input is just passed on: Note how clean WordWrap() stays. The solution is easy to understand. A developer looking at this code sometime in the future, when a new feature needs to be build in, quickly sees how long words are dealt with. Compare this to Robert C. Martin´s solution:[4] How does this solution handle long words? Long words are not even part of the domain language present in the code. At least I need considerable time to understand the approach. Admittedly the Flow Design solution with the full implementation of long word splitting is longer than Robert C. Martin´s. At least it seems. Because his solution does not cover all the “word wrap situations” the Flow Design solution handles. Some lines would need to be added to be on par, I guess. But even then… Is a difference in LOC that important as long as it´s in the same ball park? I value understandability and openness for extension higher than saving on the last line of code. Simplicity is not just less code, it´s also clarity in design. But don´t take my word for it. Try Flow Design on larger problems and compare for yourself. What´s the easier, more straightforward way to clean code? And keep in mind: You ain´t seen all yet ;-) There´s more to Flow Design than described in this chapter. In closing I hope I was able to give you a impression of functional design that makes you hungry for more. To me it´s an inevitable step in software development. Jumping from requirements to code does not scale. And it leads to dirty code all to quickly. Some thought should be invested first. Where there is a clear Entry Point visible, it´s functionality should be designed using data flows. Because with data flows abstraction is possible. For more background on why that´s necessary read my blog article here. For now let me point out to you - if you haven´t already noticed - that Flow Design is a general purpose declarative language. It´s “programming by intention” (Shalloway et al.). Just write down how you think the solution should work on a high level of abstraction. This breaks down a large problem in smaller problems. And by following the PoMO the solutions to those smaller problems are independent of each other. So they are easy to test. Or you could even think about getting them implemented in parallel by different team members. Flow Design not only increases evolvability, but also helps becoming more productive. All team members can participate in functional design. This goes beyon collective code ownership. We´re talking collective design/architecture ownership. Because with Flow Design there is a common visual language to talk about functional design - which is the foundation for all other design activities.   PS: If you like what you read, consider getting my ebook “The Incremental Architekt´s Napkin”. It´s where I compile all the articles in this series for easier reading. I like the strictness of Function Programming - but I also find it quite hard to live by. And it certainly is not what millions of programmers are used to. Also to me it seems, the real world is full of state and side effects. So why give them such a bad image? That´s why functional design takes a more pragmatic approach. State and side effects are ok for processing steps - but be sure to follow the SRP. Don´t put too much of it into a single processing step. ? Image taken from www.physioweb.org ? My code samples are written in C#. C# sports typed function pointers called delegates. Action is such a function pointer type matching functions with signature void someName(T t). Other languages provide similar ways to work with functions as first class citizens - even Java now in version 8. I trust you find a way to map this detail of my translation to your favorite programming language. I know it works for Java, C++, Ruby, JavaScript, Python, Go. And if you´re using a Functional Programming language it´s of course a no brainer. ? Taken from his blog post “The Craftsman 62, The Dark Path”. ?

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• Exporting a non public Type through public API

  - by sachin

  I am trying to follow Trees tutorial at: http://cslibrary.stanford.edu/110/BinaryTrees.html Here is the code I have written so far: package trees.bst; import java.util.ArrayList; import java.util.List; import java.util.StringTokenizer; /** * * @author sachin */ public class BinarySearchTree { Node root = null; class Node { Node left = null; Node right = null; int data = 0; public Node(int data) { this.left = null; this.right = null; this.data = data; } } public void insert(int data) { root = insert(data, root); } public boolean lookup(int data) { return lookup(data, root); } public void buildTree(int numNodes) { for (int i = 0; i < numNodes; i++) { int num = (int) (Math.random() * 10); System.out.println("Inserting number:" + num); insert(num); } } public int size() { return size(root); } public int maxDepth() { return maxDepth(root); } public int minValue() { return minValue(root); } public int maxValue() { return maxValue(root); } public void printTree() { //inorder traversal System.out.println("inorder traversal:"); printTree(root); System.out.println("\n--------------"); } public void printPostorder() { //inorder traversal System.out.println("printPostorder traversal:"); printPostorder(root); System.out.println("\n--------------"); } public int buildTreeFromOutputString(String op) { root = null; int i = 0; StringTokenizer st = new StringTokenizer(op); while (st.hasMoreTokens()) { String stNum = st.nextToken(); int num = Integer.parseInt(stNum); System.out.println("buildTreeFromOutputString: Inserting number:" + num); insert(num); i++; } return i; } public boolean hasPathSum(int pathsum) { return hasPathSum(pathsum, root); } public void mirror() { mirror(root); } public void doubleTree() { doubleTree(root); } public boolean sameTree(BinarySearchTree bst) { //is this tree same as another given tree? return sameTree(this.root, bst.getRoot()); } public void printPaths() { if (root == null) { System.out.println("print path sum: tree is empty"); } List pathSoFar = new ArrayList(); printPaths(root, pathSoFar); } ///-------------------------------------------Public helper functions public Node getRoot() { return root; } //Exporting a non public Type through public API ///-------------------------------------------Helper Functions private boolean isLeaf(Node node) { if (node == null) { return false; } if (node.left == null && node.right == null) { return true; } return false; } ///----------------------------------------------------------- private boolean sameTree(Node n1, Node n2) { if ((n1 == null && n2 == null)) { return true; } else { if ((n1 == null || n2 == null)) { return false; } else { if ((n1.data == n2.data)) { return (sameTree(n1.left, n2.left) && sameTree(n1.right, n2.right)); } } } return false; } private void doubleTree(Node node) { //create a copy //bypass the copy to continue looping if (node == null) { return; } Node copyNode = new Node(node.data); Node temp = node.left; node.left = copyNode; copyNode.left = temp; doubleTree(copyNode.left); doubleTree(node.right); } private void mirror(Node node) { if (node == null) { return; } Node temp = node.left; node.left = node.right; node.right = temp; mirror(node.left); mirror(node.right); } private void printPaths(Node node, List pathSoFar) { if (node == null) { return; } pathSoFar.add(node.data); if (isLeaf(node)) { System.out.println("path in tree:" + pathSoFar); pathSoFar.remove(pathSoFar.lastIndexOf(node.data)); //only the current node, a node.data may be duplicated return; } else { printPaths(node.left, pathSoFar); printPaths(node.right, pathSoFar); } } private boolean hasPathSum(int pathsum, Node node) { if (node == null) { return false; } int val = pathsum - node.data; boolean ret = false; if (val == 0 && isLeaf(node)) { ret = true; } else if (val == 0 && !isLeaf(node)) { ret = false; } else if (val != 0 && isLeaf(node)) { ret = false; } else if (val != 0 && !isLeaf(node)) { //recurse further ret = hasPathSum(val, node.left) || hasPathSum(val, node.right); } return ret; } private void printPostorder(Node node) { //inorder traversal if (node == null) { return; } printPostorder(node.left); printPostorder(node.right); System.out.print(" " + node.data); } private void printTree(Node node) { //inorder traversal if (node == null) { return; } printTree(node.left); System.out.print(" " + node.data); printTree(node.right); } private int minValue(Node node) { if (node == null) { //error case: this is not supported return -1; } if (node.left == null) { return node.data; } else { return minValue(node.left); } } private int maxValue(Node node) { if (node == null) { //error case: this is not supported return -1; } if (node.right == null) { return node.data; } else { return maxValue(node.right); } } private int maxDepth(Node node) { if (node == null || (node.left == null && node.right == null)) { return 0; } int ldepth = 1 + maxDepth(node.left); int rdepth = 1 + maxDepth(node.right); if (ldepth > rdepth) { return ldepth; } else { return rdepth; } } private int size(Node node) { if (node == null) { return 0; } return 1 + size(node.left) + size(node.right); } private Node insert(int data, Node node) { if (node == null) { node = new Node(data); } else if (data <= node.data) { node.left = insert(data, node.left); } else { node.right = insert(data, node.right); } //control should never reach here; return node; } private boolean lookup(int data, Node node) { if (node == null) { return false; } if (node.data == data) { return true; } if (data < node.data) { return lookup(data, node.left); } else { return lookup(data, node.right); } } public static void main(String[] args) { BinarySearchTree bst = new BinarySearchTree(); int treesize = 5; bst.buildTree(treesize); //treesize = bst.buildTreeFromOutputString("4 4 4 6 7"); treesize = bst.buildTreeFromOutputString("3 4 6 3 6"); //treesize = bst.buildTreeFromOutputString("10"); for (int i = 0; i < treesize; i++) { System.out.println("Searching:" + i + " found:" + bst.lookup(i)); } System.out.println("tree size:" + bst.size()); System.out.println("maxDepth :" + bst.maxDepth()); System.out.println("minvalue :" + bst.minValue()); System.out.println("maxvalue :" + bst.maxValue()); bst.printTree(); bst.printPostorder(); int pathSum = 10; System.out.println("hasPathSum " + pathSum + ":" + bst.hasPathSum(pathSum)); pathSum = 6; System.out.println("hasPathSum " + pathSum + ":" + bst.hasPathSum(pathSum)); pathSum = 19; System.out.println("hasPathSum " + pathSum + ":" + bst.hasPathSum(pathSum)); bst.printPaths(); bst.printTree(); //bst.mirror(); System.out.println("Tree after mirror function:"); bst.printTree(); //bst.doubleTree(); System.out.println("Tree after double function:"); bst.printTree(); System.out.println("tree size:" + bst.size()); System.out.println("Same tree:" + bst.sameTree(bst)); BinarySearchTree bst2 = new BinarySearchTree(); bst2.buildTree(treesize); treesize = bst2.buildTreeFromOutputString("3 4 6 3 6"); bst2.printTree(); System.out.println("Same tree:" + bst.sameTree(bst2)); System.out.println("---"); } } Now the problem is that netbeans shows Warning: Exporting a non public Type through public API for function getRoot(). I write this function to get root of tree to be used in sameTree() function, to help comparison of "this" with given tree. Perhaps this is a OOP design issue... How should I restructure the above code that I do not get this warning and what is the concept I am missing here?

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• Reading Data from DDFS ValueError: No JSON object could be decoded

  - by secumind

  I'm running dozens of map reduce jobs for a number of different purposes using disco. My data has grown enormous and I thought I would try using DDFS for a change rather than standard txt files. I've followed the DISCO map/reduce example Counting Words as a map/reduce job, without to much difficulty and with the help of others, Reading JSON specific data into DISCO I've gotten past one of my latest problems. I'm trying to read data in/out of ddfs to better chunk and distribute it but am having a bit of trouble. Here's an example file: file.txt {"favorited": false, "in_reply_to_user_id": null, "contributors": null, "truncated": false, "text": "I'll call him back tomorrow I guess", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": null, "entities": {"user_mentions": [], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016843603968", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/305726905/FASHION-3.png", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1818996723/image_normal.jpg", "profile_sidebar_fill_color": "292727", "is_translator": false, "id": 113532729, "profile_text_color": "000000", "followers_count": 78, "protected": false, "location": "With My Niggas In Paris!", "default_profile_image": false, "listed_count": 0, "utc_offset": -21600, "statuses_count": 6733, "description": "Made in CHINA., Educated && Making My Own $$. Fear GOD && Put Him 1st. #TeamFollowBack #TeamiPhone\n", "friends_count": 74, "profile_link_color": "b03f3f", "profile_image_url": "http://a2.twimg.com/profile_images/1818996723/image_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "1f9199", "id_str": "113532729", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/305726905/FASHION-3.png", "name": "Bee'Jay", "lang": "en", "profile_background_tile": true, "favourites_count": 19, "screen_name": "OohMyBEEsNice", "url": "http://www.bitchimpaid.org", "created_at": "Fri Feb 12 03:32:54 +0000 2010", "contributors_enabled": false, "time_zone": "Central Time (US & Canada)", "profile_sidebar_border_color": "000000", "default_profile": false, "following": null}, "in_reply_to_screen_name": null, "retweet_count": 0, "geo": null, "id": 168931016843603968, "source": "<a href=\"http://twitter.com/#!/download/iphone\" rel=\"nofollow\">Twitter for iPhone</a>"} {"favorited": false, "in_reply_to_user_id": 50940453, "contributors": null, "truncated": false, "text": "@LegaMrvica @MimozaBand makasi om artis :D kadoo kadoo", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": "168653037894770688", "coordinates": null, "in_reply_to_user_id_str": "50940453", "entities": {"user_mentions": [{"indices": [0, 11], "screen_name": "LegaMrvica", "id": 50940453, "name": "Lega_thePianis", "id_str": "50940453"}, {"indices": [12, 23], "screen_name": "MimozaBand", "id": 375128905, "name": "Mimoza", "id_str": "375128905"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": 168653037894770688, "id_str": "168931016868761600", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "profile_sidebar_fill_color": "DDFFCC", "is_translator": false, "id": 48293450, "profile_text_color": "333333", "followers_count": 182, "protected": false, "location": "\u00dcT: -6.906799,107.622383", "default_profile_image": false, "listed_count": 0, "utc_offset": -28800, "statuses_count": 3052, "description": "Fashion design maranatha '11 // traditional dancer (bali) at sanggar tampak siring & Natya Nataraja", "friends_count": 206, "profile_link_color": "0084B4", "profile_image_url": "http://a3.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "9AE4E8", "id_str": "48293450", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "name": "nana afiff", "lang": "en", "profile_background_tile": true, "favourites_count": 2, "screen_name": "hasnfebria", "url": null, "created_at": "Thu Jun 18 08:50:29 +0000 2009", "contributors_enabled": false, "time_zone": "Pacific Time (US & Canada)", "profile_sidebar_border_color": "BDDCAD", "default_profile": false, "following": null}, "in_reply_to_screen_name": "LegaMrvica", "retweet_count": 0, "geo": null, "id": 168931016868761600, "source": "<a href=\"http://blackberry.com/twitter\" rel=\"nofollow\">Twitter for BlackBerry\u00ae</a>"} {"favorited": false, "in_reply_to_user_id": 27260086, "contributors": null, "truncated": false, "text": "@justinbieber u were born to be somebody, and u're super important in beliebers' life. thanks for all biebs. I love u. follow me? 84", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": "27260086", "entities": {"user_mentions": [{"indices": [0, 13], "screen_name": "justinbieber", "id": 27260086, "name": "Justin Bieber", "id_str": "27260086"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016856178688", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/416005864/Captura.JPG", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "profile_sidebar_fill_color": "f5e7f3", "is_translator": false, "id": 406750700, "profile_text_color": "333333", "followers_count": 1122, "protected": false, "location": "Adentro de una supra.", "default_profile_image": false, "listed_count": 0, "utc_offset": -14400, "statuses_count": 20966, "description": "Mi \u00eddolo es @justinbieber , si te gusta \u00a1genial!, si no, solo respetalo. El cambi\u00f3 mi vida completamente y mi sue\u00f1o es conocerlo #TrueBelieber . ", "friends_count": 1015, "profile_link_color": "9404b8", "profile_image_url": "http://a1.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "f9fcfa", "id_str": "406750700", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/416005864/Captura.JPG", "name": "neversaynever,right?", "lang": "es", "profile_background_tile": false, "favourites_count": 22, "screen_name": "True_Belieebers", "url": "http://www.wehavebieber-fever.tumblr.com", "created_at": "Mon Nov 07 04:17:40 +0000 2011", "contributors_enabled": false, "time_zone": "Santiago", "profile_sidebar_border_color": "C0DEED", "default_profile": false, "following": null}, "in_reply_to_screen_name": "justinbieber", "retweet_count": 0, "geo": null, "id": 168931016856178688, "source": "<a href=\"http://yfrog.com\" rel=\"nofollow\">Yfrog</a>"} I load it into DDFS with: # ddfs chunk data:test1 ./file.txt created: disco://localhost/ddfs/vol0/blob/44/file_txt-0$549-db27b-125e1 I test that the file is indeed loaded into ddfs with: # ddfs xcat data:test1 {"favorited": false, "in_reply_to_user_id": null, "contributors": null, "truncated": false, "text": "I'll call him back tomorrow I guess", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": null, "entities": {"user_mentions": [], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016843603968", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/305726905/FASHION-3.png", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1818996723/image_normal.jpg", "profile_sidebar_fill_color": "292727", "is_translator": false, "id": 113532729, "profile_text_color": "000000", "followers_count": 78, "protected": false, "location": "With My Niggas In Paris!", "default_profile_image": false, "listed_count": 0, "utc_offset": -21600, "statuses_count": 6733, "description": "Made in CHINA., Educated && Making My Own $$. Fear GOD && Put Him 1st. #TeamFollowBack #TeamiPhone\n", "friends_count": 74, "profile_link_color": "b03f3f", "profile_image_url": "http://a2.twimg.com/profile_images/1818996723/image_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "1f9199", "id_str": "113532729", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/305726905/FASHION-3.png", "name": "Bee'Jay", "lang": "en", "profile_background_tile": true, "favourites_count": 19, "screen_name": "OohMyBEEsNice", "url": "http://www.bitchimpaid.org", "created_at": "Fri Feb 12 03:32:54 +0000 2010", "contributors_enabled": false, "time_zone": "Central Time (US & Canada)", "profile_sidebar_border_color": "000000", "default_profile": false, "following": null}, "in_reply_to_screen_name": null, "retweet_count": 0, "geo": null, "id": 168931016843603968, "source": "<a href=\"http://twitter.com/#!/download/iphone\" rel=\"nofollow\">Twitter for iPhone</a>"} {"favorited": false, "in_reply_to_user_id": 50940453, "contributors": null, "truncated": false, "text": "@LegaMrvica @MimozaBand makasi om artis :D kadoo kadoo", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": "168653037894770688", "coordinates": null, "in_reply_to_user_id_str": "50940453", "entities": {"user_mentions": [{"indices": [0, 11], "screen_name": "LegaMrvica", "id": 50940453, "name": "Lega_thePianis", "id_str": "50940453"}, {"indices": [12, 23], "screen_name": "MimozaBand", "id": 375128905, "name": "Mimoza", "id_str": "375128905"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": 168653037894770688, "id_str": "168931016868761600", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "profile_sidebar_fill_color": "DDFFCC", "is_translator": false, "id": 48293450, "profile_text_color": "333333", "followers_count": 182, "protected": false, "location": "\u00dcT: -6.906799,107.622383", "default_profile_image": false, "listed_count": 0, "utc_offset": -28800, "statuses_count": 3052, "description": "Fashion design maranatha '11 // traditional dancer (bali) at sanggar tampak siring & Natya Nataraja", "friends_count": 206, "profile_link_color": "0084B4", "profile_image_url": "http://a3.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "9AE4E8", "id_str": "48293450", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "name": "nana afiff", "lang": "en", "profile_background_tile": true, "favourites_count": 2, "screen_name": "hasnfebria", "url": null, "created_at": "Thu Jun 18 08:50:29 +0000 2009", "contributors_enabled": false, "time_zone": "Pacific Time (US & Canada)", "profile_sidebar_border_color": "BDDCAD", "default_profile": false, "following": null}, "in_reply_to_screen_name": "LegaMrvica", "retweet_count": 0, "geo": null, "id": 168931016868761600, "source": "<a href=\"http://blackberry.com/twitter\" rel=\"nofollow\">Twitter for BlackBerry\u00ae</a>"} {"favorited": false, "in_reply_to_user_id": 27260086, "contributors": null, "truncated": false, "text": "@justinbieber u were born to be somebody, and u're super important in beliebers' life. thanks for all biebs. I love u. follow me? 84", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": "27260086", "entities": {"user_mentions": [{"indices": [0, 13], "screen_name": "justinbieber", "id": 27260086, "name": "Justin Bieber", "id_str": "27260086"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016856178688", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/416005864/Captura.JPG", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "profile_sidebar_fill_color": "f5e7f3", "is_translator": false, "id": 406750700, "profile_text_color": "333333", "followers_count": 1122, "protected": false, "location": "Adentro de una supra.", "default_profile_image": false, "listed_count": 0, "utc_offset": -14400, "statuses_count": 20966, "description": "Mi \u00eddolo es @justinbieber , si te gusta \u00a1genial!, si no, solo respetalo. El cambi\u00f3 mi vida completamente y mi sue\u00f1o es conocerlo #TrueBelieber . ", "friends_count": 1015, "profile_link_color": "9404b8", "profile_image_url": "http://a1.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "f9fcfa", "id_str": "406750700", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/416005864/Captura.JPG", "name": "neversaynever,right?", "lang": "es", "profile_background_tile": false, "favourites_count": 22, "screen_name": "True_Belieebers", "url": "http://www.wehavebieber-fever.tumblr.com", "created_at": "Mon Nov 07 04:17:40 +0000 2011", "contributors_enabled": false, "time_zone": "Santiago", "profile_sidebar_border_color": "C0DEED", "default_profile": false, "following": null}, "in_reply_to_screen_name": "justinbieber", "retweet_count": 0, "geo": null, "id": 168931016856178688, "source": "<a href=\"http://yfrog.com\" rel=\"nofollow\">Yfrog</a> At this point everything is great, I load up the script that resulted from a previous Stack Post: from disco.core import Job, result_iterator import gzip def map(line, params): import unicodedata import json r = json.loads(line).get('text') s = unicodedata.normalize('NFD', r).encode('ascii', 'ignore') for word in s.split(): yield word, 1 def reduce(iter, params): from disco.util import kvgroup for word, counts in kvgroup(sorted(iter)): yield word, sum(counts) if __name__ == '__main__': job = Job().run(input=["tag://data:test1"], map=map, reduce=reduce) for word, count in result_iterator(job.wait(show=True)): print word, count NOTE: That this script runs file if the input=["file.txt"], however when I run it with "tag://data:test1" I get the following error: # DISCO_EVENTS=1 python count_normal_words.py Job@549:db30e:25bd8: Status: [map] 0 waiting, 1 running, 0 done, 0 failed 2012/11/25 21:43:26 master New job initialized! 2012/11/25 21:43:26 master Starting job 2012/11/25 21:43:26 master Starting map phase 2012/11/25 21:43:26 master map:0 assigned to solice 2012/11/25 21:43:26 master ERROR: Job failed: Worker at 'solice' died: Traceback (most recent call last): File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/__init__.py", line 329, in main job.worker.start(task, job, **jobargs) File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/__init__.py", line 290, in start self.run(task, job, **jobargs) File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/classic/worker.py", line 286, in run getattr(self, task.mode)(task, params) File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/classic/worker.py", line 299, in map for key, val in self['map'](entry, params): File "count_normal_words.py", line 12, in map File "/usr/lib64/python2.7/json/__init__.py", line 326, in loads return _default_decoder.decode(s) File "/usr/lib64/python2.7/json/decoder.py", line 366, in decode obj, end = self.raw_decode(s, idx=_w(s, 0).end()) File "/usr/lib64/python2.7/json/decoder.py", line 384, in raw_decode raise ValueError("No JSON object could be decoded") ValueError: No JSON object could be decoded 2012/11/25 21:43:26 master WARN: Job killed Status: [map] 1 waiting, 0 running, 0 done, 1 failed Traceback (most recent call last): File "count_normal_words.py", line 28, in <module> for word, count in result_iterator(job.wait(show=True)): File "/usr/local/lib/python2.7/site-packages/disco/core.py", line 348, in wait timeout, poll_interval * 1000) File "/usr/local/lib/python2.7/site-packages/disco/core.py", line 309, in check_results raise JobError(Job(name=jobname, master=self), "Status %s" % status) disco.error.JobError: Job Job@549:db30e:25bd8 failed: Status dead The Error states: ValueError: No JSON object could be decoded. Again, this works fine using the text file as input but now DDFS. Any ideas, I'm open to suggestions?

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• Java Simple Calculator

  - by Lahiru Kavinda

  I have made this calculator program in Java. This works well only when two numbers are calculated at one time. That means to get the sum of 1+2+3 you have to go this way : press 1 press + press 2 press = press + press 3 press = and it calculates it as 6. But I want to program this so that I can get the answer by: press 1 press + press 2 press + press 3 press = but this gives the answer 5!!! How to code this so that it works like an ordinary calculator? Here is my code: import java.awt.*; import java.awt.event.*; import javax.swing.*; public class cal1 extends JFrame { double op1 = 0d, op2 = 0d; double result = 0d; char action; boolean b = false; boolean pressequal = false; public cal1() { makeUI(); } private void makeUI() { setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setSize(400, 400); b0 = new JButton("0"); b1 = new JButton("1"); b2 = new JButton("2"); b3 = new JButton("3"); b4 = new JButton("4"); b5 = new JButton("5"); b6 = new JButton("6"); b7 = new JButton("7"); b8 = new JButton("8"); b9 = new JButton("9"); bDot = new JButton("."); bMul = new JButton("*"); bDiv = new JButton("/"); bPlus = new JButton("+"); bMinus = new JButton("-"); bEq = new JButton("="); t = new JTextField(12); t.setFont(new Font("Tahoma", Font.PLAIN, 24)); t.setHorizontalAlignment(JTextField.RIGHT); numpad = new JPanel(); display = new JPanel(); numpad.add(b7); numpad.add(b8); numpad.add(b9); numpad.add(bMul); numpad.add(b4); numpad.add(b5); numpad.add(b6); numpad.add(bDiv); numpad.add(b1); numpad.add(b2); numpad.add(b3); numpad.add(bMinus); numpad.add(bDot); numpad.add(b0); numpad.add(bEq); numpad.add(bPlus); numpad.setLayout(new GridLayout(4, 5, 5, 4)); display.add(t); add(display, BorderLayout.NORTH); add(numpad, BorderLayout.CENTER); t.addKeyListener(new KeyAdapter() { @Override public void keyTyped(KeyEvent e) { typeOnt(e); } }); b0.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b0pressed(e); } }); b1.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b1pressed(e); } }); b2.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b2pressed(e); } }); b3.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b3pressed(e); } }); b4.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b4pressed(e); } }); b5.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b5pressed(e); } }); b6.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b6pressed(e); } }); b7.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b7pressed(e); } }); b8.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b8pressed(e); } }); b9.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b9pressed(e); } }); bDot.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bDotpressed(e); } }); bPlus.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bPlusPressed(e); } }); bMinus.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bMinusPressed(e); } }); bMul.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bMulPressed(e); } }); bDiv.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bDivPressed(e); } }); bEq.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bEqpressed(e); } }); } void typeOnt(KeyEvent e) { e.consume(); } void b0pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "0"); } else { t.setText(t.getText() + "0"); } } void b1pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "1"); } else { t.setText(t.getText() + "1"); } } void b2pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "2"); } else { t.setText(t.getText() + "2"); } } void b3pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "3"); } else { t.setText(t.getText() + "3"); } } void b4pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "4"); } else { t.setText(t.getText() + "4"); } } void b5pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "5"); } else { t.setText(t.getText() + "5"); } } void b6pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "6"); } else { t.setText(t.getText() + "6"); } } void b7pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "7"); } else { t.setText(t.getText() + "7"); } } void b8pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "8"); } else { t.setText(t.getText() + "8"); } } void b9pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "9"); } else { t.setText(t.getText() + "9"); } } void bDotpressed(ActionEvent e) { if (!t.getText().contains(".")) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "0."); } else if (t.getText().isEmpty()) { t.setText("0."); } else { t.setText(t.getText() + "."); } } } void bPlusPressed(ActionEvent e) { b = true; action = '+'; op1 = Double.parseDouble(t.getText()); } void bMinusPressed(ActionEvent e) { b = true; action = '-'; op1 = Double.parseDouble(t.getText()); } void bMulPressed(ActionEvent e) { b = true; action = '*'; op1 = Double.parseDouble(t.getText()); } void bDivPressed(ActionEvent e) { b = true; action = '/'; op1 = Double.parseDouble(t.getText()); } void bEqpressed(ActionEvent e) { op2 = Double.parseDouble(t.getText()); doCal(); } void doCal() { switch (action) { case '+': result = op1 + op2; break; case '-': result = op1 - op2; break; case '*': result = op1 * op2; break; case '/': result = op1 / op2; break; } t.setText(String.valueOf(result)); } public static void main(String[] args) { new cal1().setVisible(true); } JButton b0; JButton b1; JButton b2; JButton b3; JButton b4; JButton b5; JButton b6; JButton b7; JButton b8; JButton b9; JButton bDot; JButton bPlus; JButton bMinus; JButton bMul; JButton bDiv; JButton bEq; JPanel display; JPanel numpad; JTextField t; }

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• Retrieving saved checkboxes' name and values from database

  - by sermed

  I have a form with checkboxes, each one has a value. When the registered user select any checkbox the value is incremented (the summation) and then then registred user save his selection of checkbox if he satisfied with the result of summation into database all this work fine ...i want to enable the registred user to view his selection history by retriving and displaying the checkboxes he selected in a page with thier values ... How I can do that? I'm just able to save the selected checkboxes as choice 1, choice 2, for example .. I want to view the selected checkboxes that is saved in database as the appear in the page when the user first select them: for example if the registred user selects these 3 options LEAD DEEP KEEL (1825) FULLY BATTENED MAINSAIL (558) TEAK SIDE DECKS (2889) They will be saved as for example (choice1, choice2, choice3). But if he want to view selected checkboxes the appear exactly as first he selects them: LEAD DEEP KEEL (1825) FULLY BATTENED MAINSAIL (558) TEAK SIDE DECKS (2889) This is my user table: $query="CREATE TABLE User( user_id varchar(20), password varchar(40), user_type varchar(20), firstname varchar(30), lastname varchar(30), street varchar(50), city varchar(50), county varchar(50), post_code varchar(10), country varchar(50), gender varchar(6), dob varchar(15), tel_no varchar(50), vals varchar(50), email varchar(50))"; and the code to inser the options selected to database <?php include("databaseconnection.php"); $str = ''; foreach($_POST as $key => $val) if (strpos($key,'choice') !== false) $str .= $key.','; $query = "INSERT INTO User (vals) VALUES('$str')"; $result=mysql_query($query,$conn); if ($result) { (mysql_error(); } else { echo " done"; } ?> And this is my form: function checkTotal() { document.listForm.total.value = ''; var sum = 0; for (i=0;i <form name="listForm" method="post" action="insert_options.php" > <TABLE cellPadding=3 width=600 border=0> <TBODY> <TR> <TH align=left width="87%" bgColor=#b0b3b4><SPAN class=whiteText>Item</SPAN></TH> <TH align=right width="13%" bgColor=#b0b3b4><SPAN class=whiteText>Select</SPAN></TH></TR> <TR> <TD bgcolor="#9da8af"colSpan=2><SPAN class=normalText><B>General</B></SPAN></TD></TR> <TR> <TD bgcolor="#c4c8ca"><SPAN class=normalText >TEAK SIDE DECKS (2889)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="2889" type="checkbox" onchange="checkTotal()" /></TD></TR> <TR> <TD bgColor=#c4c8ca><SPAN class=normalText>LEAD DEEP KEEL (1825)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="1825" type="checkbox" onchange="checkTotal()"></TD></TR> <TR> <TD bgColor=#c4c8ca><SPAN class=normalText>FULLY BATTENED MAINSAIL (558)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="558" type="checkbox" onchange="checkTotal()"></TD></TR> <TR> <TD bgColor=#c4c8ca><SPAN class=normalText>HIGH TECH SAILS FOR CONVENTIONAL RIG (1979)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="1979" type="checkbox" onchange="checkTotal()"></TD></TR> <TR> <TD bgColor=#c4c8ca><SPAN class=normalText>IN MAST REEFING WITH HIGH TECH SAILS (2539)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="2539" type="checkbox" onchange="checkTotal()"></TD></TR> <TR> <TD bgColor=#c4c8ca><SPAN class=normalText>SPlNNAKER GEAR (POLE LINES DECK FITTINGS) (820)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="820" type="checkbox" onchange="checkTotal()"></TD></TR> <TR> <TD bgColor=#c4c8ca><SPAN class=normalText>SPINNAKER POLE VERTICAL STOWAGE SYSTEM (214)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="214" type="checkbox" onchange="checkTotal()"></TD></TR> <TR> <TD bgColor=#c4c8ca><SPAN class=normalText>GAS ROD KICKER (208)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" 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value="701" type="checkbox" onchange="checkTotal()"></TD></TR> <TR> <TD bgcolor="#9da8af"colSpan=2><SPAN class=normalText><B>NAVIGATION ELECTRONICS & ELECTRICS</B></SPAN></TD></TR> <TD bgColor=#c4c8ca><SPAN class=normalText>VHF RADIO AERIAL CABLED TO NAVIGATION AREA(178)</SPAN></TD> <TD align=right bgColor=#c4c8ca><input name="choice" value="178" type="checkbox" onchange="checkTotal()"></TD></TR> </table>

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• JGoodies HashMap

  - by JohnMcClane

  Hi, I'm trying to build a chart program using presentation model. Using JGoodies for data binding was relatively easy for simple types like strings or numbers. But I can't figure out how to use it on a hashmap. I'll try to explain how the chart works and what my problem is: A chart consists of DataSeries, a DataSeries consists of DataPoints. I want to have a data model and to be able to use different views on the same model (e.g. bar chart, pie chart,...). Each of them consists of three classes. For example: DataPointModel: holds the data model (value, label, category) DataPointViewModel: extends JGoodies PresentationModel. wraps around DataPointModel and holds view properties like font and color. DataPoint: abstract class, extends JComponent. Different Views must subclass and implement their own ui. Binding and creating the data model was easy, but i don't know how to bind my data series model. package at.onscreen.chart; import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; import java.beans.PropertyVetoException; import java.util.Collection; import java.util.HashMap; import java.util.Iterator; public class DataSeriesModel { public static String PROPERTY_DATAPOINT = "dataPoint"; public static String PROPERTY_DATAPOINTS = "dataPoints"; public static String PROPERTY_LABEL = "label"; public static String PROPERTY_MAXVALUE = "maxValue"; /** * holds the data points */ private HashMap dataPoints; /** * the label for the data series */ private String label; /** * the maximum data point value */ private Double maxValue; /** * the model supports property change notification */ private PropertyChangeSupport propertyChangeSupport; /** * default constructor */ public DataSeriesModel() { this.maxValue = Double.valueOf(0); this.dataPoints = new HashMap(); this.propertyChangeSupport = new PropertyChangeSupport(this); } /** * constructor * @param label - the series label */ public DataSeriesModel(String label) { this.dataPoints = new HashMap(); this.maxValue = Double.valueOf(0); this.label = label; this.propertyChangeSupport = new PropertyChangeSupport(this); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public DataSeriesModel(String label, DataPoint[] dataPoints) { this.dataPoints = new HashMap(); this.propertyChangeSupport = new PropertyChangeSupport(this); this.maxValue = Double.valueOf(0); this.label = label; for (int i = 0; i < dataPoints.length; i++) { this.addDataPoint(dataPoints[i]); } } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public DataSeriesModel(String label, Collection dataPoints) { this.dataPoints = new HashMap(); this.propertyChangeSupport = new PropertyChangeSupport(this); this.maxValue = Double.valueOf(0); this.label = label; for (Iterator it = dataPoints.iterator(); it.hasNext();) { this.addDataPoint(it.next()); } } /** * adds a new data point to the series. if the series contains a data point with same id, it will be replaced by the new one. * @param dataPoint - the data point */ public void addDataPoint(DataPoint dataPoint) { String category = dataPoint.getCategory(); DataPoint oldDataPoint = this.getDataPoint(category); this.dataPoints.put(category, dataPoint); this.setMaxValue(Math.max(this.maxValue, dataPoint.getValue())); this.propertyChangeSupport.firePropertyChange(PROPERTY_DATAPOINT, oldDataPoint, dataPoint); } /** * returns the data point with given id or null if not found * @param uid - the id of the data point * @return the data point or null if there is no such point in the table */ public DataPoint getDataPoint(String category) { return this.dataPoints.get(category); } /** * removes the data point with given id from the series, if present * @param category - the data point to remove */ public void removeDataPoint(String category) { DataPoint dataPoint = this.getDataPoint(category); this.dataPoints.remove(category); if (dataPoint != null) { if (dataPoint.getValue() == this.getMaxValue()) { Double maxValue = Double.valueOf(0); for (Iterator it = this.iterator(); it.hasNext();) { DataPoint itDataPoint = it.next(); maxValue = Math.max(itDataPoint.getValue(), maxValue); } this.setMaxValue(maxValue); } } this.propertyChangeSupport.firePropertyChange(PROPERTY_DATAPOINT, dataPoint, null); } /** * removes all data points from the series * @throws PropertyVetoException */ public void removeAll() { this.setMaxValue(Double.valueOf(0)); this.dataPoints.clear(); this.propertyChangeSupport.firePropertyChange(PROPERTY_DATAPOINTS, this.getDataPoints(), null); } /** * returns the maximum of all data point values * @return the maximum of all data points */ public Double getMaxValue() { return this.maxValue; } /** * sets the max value * @param maxValue - the max value */ protected void setMaxValue(Double maxValue) { Double oldMaxValue = this.getMaxValue(); this.maxValue = maxValue; this.propertyChangeSupport.firePropertyChange(PROPERTY_MAXVALUE, oldMaxValue, maxValue); } /** * returns true if there is a data point with given category * @param category - the data point category * @return true if there is a data point with given category, otherwise false */ public boolean contains(String category) { return this.dataPoints.containsKey(category); } /** * returns the label for the series * @return the label for the series */ public String getLabel() { return this.label; } /** * returns an iterator over the data points * @return an iterator over the data points */ public Iterator iterator() { return this.dataPoints.values().iterator(); } /** * returns a collection of the data points. the collection supports removal, but does not support adding of data points. * @return a collection of data points */ public Collection getDataPoints() { return this.dataPoints.values(); } /** * returns the number of data points in the series * @return the number of data points */ public int getSize() { return this.dataPoints.size(); } /** * adds a PropertyChangeListener * @param listener - the listener */ public void addPropertyChangeListener(PropertyChangeListener listener) { this.propertyChangeSupport.addPropertyChangeListener(listener); } /** * removes a PropertyChangeListener * @param listener - the listener */ public void removePropertyChangeListener(PropertyChangeListener listener) { this.propertyChangeSupport.removePropertyChangeListener(listener); } } package at.onscreen.chart; import java.beans.PropertyVetoException; import java.util.Collection; import java.util.Iterator; import com.jgoodies.binding.PresentationModel; public class DataSeriesViewModel extends PresentationModel { /** * default constructor */ public DataSeriesViewModel() { super(new DataSeriesModel()); } /** * constructor * @param label - the series label */ public DataSeriesViewModel(String label) { super(new DataSeriesModel(label)); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public DataSeriesViewModel(String label, DataPoint[] dataPoints) { super(new DataSeriesModel(label, dataPoints)); } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public DataSeriesViewModel(String label, Collection dataPoints) { super(new DataSeriesModel(label, dataPoints)); } /** * full constructor * @param model - the data series model */ public DataSeriesViewModel(DataSeriesModel model) { super(model); } /** * adds a data point to the series * @param dataPoint - the data point */ public void addDataPoint(DataPoint dataPoint) { this.getBean().addDataPoint(dataPoint); } /** * returns true if there is a data point with given category * @param category - the data point category * @return true if there is a data point with given category, otherwise false */ public boolean contains(String category) { return this.getBean().contains(category); } /** * returns the data point with given id or null if not found * @param uid - the id of the data point * @return the data point or null if there is no such point in the table */ public DataPoint getDataPoint(String category) { return this.getBean().getDataPoint(category); } /** * returns a collection of the data points. the collection supports removal, but does not support adding of data points. * @return a collection of data points */ public Collection getDataPoints() { return this.getBean().getDataPoints(); } /** * returns the label for the series * @return the label for the series */ public String getLabel() { return this.getBean().getLabel(); } /** * sets the max value * @param maxValue - the max value */ public Double getMaxValue() { return this.getBean().getMaxValue(); } /** * returns the number of data points in the series * @return the number of data points */ public int getSize() { return this.getBean().getSize(); } /** * returns an iterator over the data points * @return an iterator over the data points */ public Iterator iterator() { return this.getBean().iterator(); } /** * removes all data points from the series * @throws PropertyVetoException */ public void removeAll() { this.getBean().removeAll(); } /** * removes the data point with given id from the series, if present * @param category - the data point to remove */ public void removeDataPoint(String category) { this.getBean().removeDataPoint(category); } } package at.onscreen.chart; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.beans.PropertyVetoException; import java.util.Collection; import java.util.Iterator; import javax.swing.JComponent; public abstract class DataSeries extends JComponent implements PropertyChangeListener { /** * the model */ private DataSeriesViewModel model; /** * default constructor */ public DataSeries() { this.model = new DataSeriesViewModel(); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * constructor * @param label - the series label */ public DataSeries(String label) { this.model = new DataSeriesViewModel(label); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public DataSeries(String label, DataPoint[] dataPoints) { this.model = new DataSeriesViewModel(label, dataPoints); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public DataSeries(String label, Collection dataPoints) { this.model = new DataSeriesViewModel(label, dataPoints); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * full constructor * @param model - the model */ public DataSeries(DataSeriesViewModel model) { this.model = model; this.model.addPropertyChangeListener(this); this.createComponents(); } /** * creates, binds and configures UI components. * data point properties can be created here as components or be painted in paintComponent. */ protected abstract void createComponents(); @Override public void propertyChange(PropertyChangeEvent evt) { this.repaint(); } /** * adds a data point to the series * @param dataPoint - the data point */ public void addDataPoint(DataPoint dataPoint) { this.model.addDataPoint(dataPoint); } /** * returns true if there is a data point with given category * @param category - the data point category * @return true if there is a data point with given category, otherwise false */ public boolean contains(String category) { return this.model.contains(category); } /** * returns the data point with given id or null if not found * @param uid - the id of the data point * @return the data point or null if there is no such point in the table */ public DataPoint getDataPoint(String category) { return this.model.getDataPoint(category); } /** * returns a collection of the data points. the collection supports removal, but does not support adding of data points. * @return a collection of data points */ public Collection getDataPoints() { return this.model.getDataPoints(); } /** * returns the label for the series * @return the label for the series */ public String getLabel() { return this.model.getLabel(); } /** * sets the max value * @param maxValue - the max value */ public Double getMaxValue() { return this.model.getMaxValue(); } /** * returns the number of data points in the series * @return the number of data points */ public int getDataPointCount() { return this.model.getSize(); } /** * returns an iterator over the data points * @return an iterator over the data points */ public Iterator iterator() { return this.model.iterator(); } /** * removes all data points from the series * @throws PropertyVetoException */ public void removeAll() { this.model.removeAll(); } /** * removes the data point with given id from the series, if present * @param category - the data point to remove */ public void removeDataPoint(String category) { this.model.removeDataPoint(category); } /** * returns the data series view model * @return - the data series view model */ public DataSeriesViewModel getViewModel() { return this.model; } /** * returns the data series model * @return - the data series model */ public DataSeriesModel getModel() { return this.model.getBean(); } } package at.onscreen.chart.builder; import java.util.Collection; import net.miginfocom.swing.MigLayout; import at.onscreen.chart.DataPoint; import at.onscreen.chart.DataSeries; import at.onscreen.chart.DataSeriesViewModel; public class BuilderDataSeries extends DataSeries { /** * default constructor */ public BuilderDataSeries() { super(); } /** * constructor * @param label - the series label */ public BuilderDataSeries(String label) { super(label); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public BuilderDataSeries(String label, DataPoint[] dataPoints) { super(label, dataPoints); } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public BuilderDataSeries(String label, Collection dataPoints) { super(label, dataPoints); } /** * full constructor * @param model - the model */ public BuilderDataSeries(DataSeriesViewModel model) { super(model); } @Override protected void createComponents() { this.setLayout(new MigLayout()); /* * * I want to add a new BuilderDataPoint for each data point in the model. * I want the BuilderDataPoints to be synchronized with the model. * e.g. when a data point is removed from the model, the BuilderDataPoint shall be removed * from the BuilderDataSeries * */ } } package at.onscreen.chart.builder; import javax.swing.JFormattedTextField; import javax.swing.JTextField; import at.onscreen.chart.DataPoint; import at.onscreen.chart.DataPointModel; import at.onscreen.chart.DataPointViewModel; import at.onscreen.chart.ValueFormat; import com.jgoodies.binding.adapter.BasicComponentFactory; import com.jgoodies.binding.beans.BeanAdapter; public class BuilderDataPoint extends DataPoint { /** * default constructor */ public BuilderDataPoint() { super(); } /** * constructor * @param category - the category */ public BuilderDataPoint(String category) { super(category); } /** * constructor * @param value - the value * @param label - the label * @param category - the category */ public BuilderDataPoint(Double value, String label, String category) { super(value, label, category); } /** * full constructor * @param model - the model */ public BuilderDataPoint(DataPointViewModel model) { super(model); } @Override protected void createComponents() { BeanAdapter beanAdapter = new BeanAdapter(this.getModel(), true); ValueFormat format = new ValueFormat(); JFormattedTextField value = BasicComponentFactory.createFormattedTextField(beanAdapter.getValueModel(DataPointModel.PROPERTY_VALUE), format); this.add(value, "w 80, growx, wrap"); JTextField label = BasicComponentFactory.createTextField(beanAdapter.getValueModel(DataPointModel.PROPERTY_LABEL)); this.add(label, "growx, wrap"); JTextField category = BasicComponentFactory.createTextField(beanAdapter.getValueModel(DataPointModel.PROPERTY_CATEGORY)); this.add(category, "growx, wrap"); } } To sum it up: I need to know how to bind a hash map property to JComponent.components property. JGoodies is in my opinion not very well documented, I spent a long time searching through the internet, but I did not find any solution to my problem. Hope you can help me.

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• Java code optimization on matrix windowing computes in more time

  - by rano

  I have a matrix which represents an image and I need to cycle over each pixel and for each one of those I have to compute the sum of all its neighbors, ie the pixels that belong to a window of radius rad centered on the pixel. I came up with three alternatives: The simplest way, the one that recomputes the window for each pixel The more optimized way that uses a queue to store the sums of the window columns and cycling through the columns of the matrix updates this queue by adding a new element and removing the oldes The even more optimized way that does not need to recompute the queue for each row but incrementally adjusts a previously saved one I implemented them in c++ using a queue for the second method and a combination of deques for the third (I need to iterate through their elements without destructing them) and scored their times to see if there was an actual improvement. it appears that the third method is indeed faster. Then I tried to port the code to Java (and I must admit that I'm not very comfortable with it). I used ArrayDeque for the second method and LinkedLists for the third resulting in the third being inefficient in time. Here is the simplest method in C++ (I'm not posting the java version since it is almost identical): void normalWindowing(int mat[][MAX], int cols, int rows, int rad){ int i, j; int h = 0; for (i = 0; i < rows; ++i) { for (j = 0; j < cols; j++) { h = 0; for (int ry =- rad; ry <= rad; ry++) { int y = i + ry; if (y >= 0 && y < rows) { for (int rx =- rad; rx <= rad; rx++) { int x = j + rx; if (x >= 0 && x < cols) { h += mat[y][x]; } } } } } } } Here is the second method (the one optimized through columns) in C++: void opt1Windowing(int mat[][MAX], int cols, int rows, int rad){ int i, j, h, y, col; queue<int>* q = NULL; for (i = 0; i < rows; ++i) { if (q != NULL) delete(q); q = new queue<int>(); h = 0; for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][rx]; } } q->push(mem); h += mem; } } for (j = 1; j < cols; j++) { col = j + rad; if (j - rad > 0) { h -= q->front(); q->pop(); } if (j + rad < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][col]; } } q->push(mem); h += mem; } } } } And here is the Java version: public static void opt1Windowing(int [][] mat, int rad){ int i, j = 0, h, y, col; int cols = mat[0].length; int rows = mat.length; ArrayDeque<Integer> q = null; for (i = 0; i < rows; ++i) { q = new ArrayDeque<Integer>(); h = 0; for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][rx]; } } q.addLast(mem); h += mem; } } j = 0; for (j = 1; j < cols; j++) { col = j + rad; if (j - rad > 0) { h -= q.peekFirst(); q.pop(); } if (j + rad < cols) { int mem = 0; for (int ry =- rad; ry <= rad; ry++) { y = i + ry; if (y >= 0 && y < rows) { mem += mat[y][col]; } } q.addLast(mem); h += mem; } } } } I recognize this post will be a wall of text. Here is the third method in C++: void opt2Windowing(int mat[][MAX], int cols, int rows, int rad){ int i = 0; int j = 0; int h = 0; int hh = 0; deque< deque<int> *> * M = new deque< deque<int> *>(); for (int ry = 0; ry <= rad; ry++) { if (ry < rows) { deque<int> * q = new deque<int>(); M->push_back(q); for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int val = mat[ry][rx]; q->push_back(val); h += val; } } } } deque<int> * C = new deque<int>(M->front()->size()); deque<int> * Q = new deque<int>(M->front()->size()); deque<int> * R = new deque<int>(M->size()); deque< deque<int> *>::iterator mit; deque< deque<int> *>::iterator mstart = M->begin(); deque< deque<int> *>::iterator mend = M->end(); deque<int>::iterator rit; deque<int>::iterator rstart = R->begin(); deque<int>::iterator rend = R->end(); deque<int>::iterator cit; deque<int>::iterator cstart = C->begin(); deque<int>::iterator cend = C->end(); for (mit = mstart, rit = rstart; mit != mend, rit != rend; ++mit, ++rit) { deque<int>::iterator pit; deque<int>::iterator pstart = (* mit)->begin(); deque<int>::iterator pend = (* mit)->end(); for(cit = cstart, pit = pstart; cit != cend && pit != pend; ++cit, ++pit) { (* cit) += (* pit); (* rit) += (* pit); } } for (i = 0; i < rows; ++i) { j = 0; if (i - rad > 0) { deque<int>::iterator cit; deque<int>::iterator cstart = C->begin(); deque<int>::iterator cend = C->end(); deque<int>::iterator pit; deque<int>::iterator pstart = (M->front())->begin(); deque<int>::iterator pend = (M->front())->end(); for(cit = cstart, pit = pstart; cit != cend; ++cit, ++pit) { (* cit) -= (* pit); } deque<int> * k = M->front(); M->pop_front(); delete k; h -= R->front(); R->pop_front(); } int row = i + rad; if (row < rows && i > 0) { deque<int> * newQ = new deque<int>(); M->push_back(newQ); deque<int>::iterator cit; deque<int>::iterator cstart = C->begin(); deque<int>::iterator cend = C->end(); int rx; int tot = 0; for (rx = 0, cit = cstart; rx <= rad; rx++, ++cit) { if (rx < cols) { int val = mat[row][rx]; newQ->push_back(val); (* cit) += val; tot += val; } } R->push_back(tot); h += tot; } hh = h; copy(C->begin(), C->end(), Q->begin()); for (j = 1; j < cols; j++) { int col = j + rad; if (j - rad > 0) { hh -= Q->front(); Q->pop_front(); } if (j + rad < cols) { int val = 0; for (int ry =- rad; ry <= rad; ry++) { int y = i + ry; if (y >= 0 && y < rows) { val += mat[y][col]; } } hh += val; Q->push_back(val); } } } } And finally its Java version: public static void opt2Windowing(int [][] mat, int rad){ int cols = mat[0].length; int rows = mat.length; int i = 0; int j = 0; int h = 0; int hh = 0; LinkedList<LinkedList<Integer>> M = new LinkedList<LinkedList<Integer>>(); for (int ry = 0; ry <= rad; ry++) { if (ry < rows) { LinkedList<Integer> q = new LinkedList<Integer>(); M.addLast(q); for (int rx = 0; rx <= rad; rx++) { if (rx < cols) { int val = mat[ry][rx]; q.addLast(val); h += val; } } } } int firstSize = M.getFirst().size(); int mSize = M.size(); LinkedList<Integer> C = new LinkedList<Integer>(); LinkedList<Integer> Q = null; LinkedList<Integer> R = new LinkedList<Integer>(); for (int k = 0; k < firstSize; k++) { C.add(0); } for (int k = 0; k < mSize; k++) { R.add(0); } ListIterator<LinkedList<Integer>> mit; ListIterator<Integer> rit; ListIterator<Integer> cit; ListIterator<Integer> pit; for (mit = M.listIterator(), rit = R.listIterator(); mit.hasNext();) { Integer r = rit.next(); int rsum = 0; for (cit = C.listIterator(), pit = (mit.next()).listIterator(); cit.hasNext();) { Integer c = cit.next(); Integer p = pit.next(); rsum += p; cit.set(c + p); } rit.set(r + rsum); } for (i = 0; i < rows; ++i) { j = 0; if (i - rad > 0) { for(cit = C.listIterator(), pit = M.getFirst().listIterator(); cit.hasNext();) { Integer c = cit.next(); Integer p = pit.next(); cit.set(c - p); } M.removeFirst(); h -= R.getFirst(); R.removeFirst(); } int row = i + rad; if (row < rows && i > 0) { LinkedList<Integer> newQ = new LinkedList<Integer>(); M.addLast(newQ); int rx; int tot = 0; for (rx = 0, cit = C.listIterator(); rx <= rad; rx++) { if (rx < cols) { Integer c = cit.next(); int val = mat[row][rx]; newQ.addLast(val); cit.set(c + val); tot += val; } } R.addLast(tot); h += tot; } hh = h; Q = new LinkedList<Integer>(); Q.addAll(C); for (j = 1; j < cols; j++) { int col = j + rad; if (j - rad > 0) { hh -= Q.getFirst(); Q.pop(); } if (j + rad < cols) { int val = 0; for (int ry =- rad; ry <= rad; ry++) { int y = i + ry; if (y >= 0 && y < rows) { val += mat[y][col]; } } hh += val; Q.addLast(val); } } } } I guess that most is due to the poor choice of the LinkedList in Java and to the lack of an efficient (not shallow) copy method between two LinkedList. How can I improve the third Java method? Am I doing some conceptual error? As always, any criticisms is welcome. UPDATE Even if it does not solve the issue, using ArrayLists, as being suggested, instead of LinkedList improves the third method. The second one performs still better (but when the number of rows and columns of the matrix is lower than 300 and the window radius is small the first unoptimized method is the fastest in Java)

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