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• PostgreSQL: Auto-partition a table

  - by Adam Matan

  Hi, I have a huge database which holds pairs of numbers (A,B), each ranging from 0 to 10,000 and stored as floats. e.g., (1, 9984.4), (2143.44, 124.243), (0.55, 0), ... Since the PostgreSQL table which stores these pairs grew quite large, I have decided to partition it into inheriting sub-tables. I intend to create 100 such tables, each storing a range of 1000x1000. The problem is that these numbers tend to come in large chunks of nearby numbers. It means that in the future, some tables will be nearly empty and some will hold a very large portion of the database. Unfortunately, the distribution of future pairs is yet unknown. I am looking for a way to automatically repartition my table. That means that if a certain subtable holds more than a specific number of pairs, it will be automatically partitioned into four sub-sub tables, and so on. My questions are: Is recursive partitioning and inheritance possible in PostgreSQL 8.3? Will indexes and query plans understand it? What's the best way to split a subtable once it grew too large? I should point out that this isn't a live database, so a downtime of few hours every week is totally acceptable. Thanks in advance, Adam

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• Beginner problems with references to arrays in python 3.1.1

  - by Protean

  As part of the last assignment in a beginner python programing class, I have been assigned a traveling sales man problem. I settled on a recursive function to find each permutation and the sum of the distances between the destinations, however, I am have a lot of problems with references. Arrays in different instances of the Permute and Main functions of TSP seem to be pointing to the same reference. from math import sqrt class TSP: def __init__(self): self.CartisianCoordinates = [['A',[1,1]], ['B',[2,2]], ['C',[2,1]], ['D',[1,2]], ['E',[3,3]]] self.Array = [] self.Max = 0 self.StoredList = ['',0] def Distance(self, i1, i2): x1 = self.CartisianCoordinates[i1][1][0] y1 = self.CartisianCoordinates[i1][1][1] x2 = self.CartisianCoordinates[i2][1][0] y2 = self.CartisianCoordinates[i2][1][1] return sqrt(pow((x2 - x1), 2) + pow((y2 - y1), 2)) def Evaluate(self): temparray = [] Data = [] for i in range(len(self.CartisianCoordinates)): Data.append([]) for i1 in range(len(self.CartisianCoordinates)): for i2 in range(len(self.CartisianCoordinates)): if i1 != i2: temparray.append(self.Distance(i1, i2)) else: temparray.append('X') Data[i1] = temparray temparray = [] self.Array = Data self.Max = len(Data) def Permute(self,varray,index,vcarry,mcarry): #Problem Class array = varray[:] carry = vcarry[:] for i in range(self.Max): print ('ARRAY:', array) print (index,i,carry,array[index][i]) if array[index][i] != 'X': carry[0] += self.CartisianCoordinates[i][0] carry[1] += array[index][i] if len(carry) != self.Max: temparray = array[:] for j in range(self.Max):temparray[j][i] = 'X' index = i mcarry += self.Permute(temparray,index,carry,mcarry) else: return mcarry print ('pass',mcarry) return mcarry def Main(self): out = [] self.Evaluate() for i in range(self.Max): array = self.Array[:] #array appears to maintain the same reference after each copy, resulting in an incorrect array being passed to Permute after the first iteration. print (self.Array[:]) for j in range(self.Max):array[j][i] = 'X' print('I:', i, array) out.append(self.Permute(array,i,[str(self.CartisianCoordinates[i][0]),0],[])) return out SalesPerson = TSP() print(SalesPerson.Main()) It would be greatly appreciated if you could provide me with help in solving the reference problems I am having. Thank you.

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• StackOverFlowException - but oviously NO recursion/endless loop

  - by user567706

  Hi there, I'm now blocked by this problem the entire day, read thousands of google results, but nothing seems to reflect my problem or even come near to it... i hope any of you has a push into the right direction for me. I wrote a client-server-application (so more like 2 applications) - the client collects data about his system, as well as a screenshot, serializes all this into a XML stream (the picture as a byte[]-array]) and sends this to the server in regular intervals. The server receives the stream (via tcp), deserializes the xml to an information-object and shows the information on a windows form. This process is running stable for about 20-25 minutes at a submission interval of 3 seconds. When observing the memory usage there's nothing significant to see, also kinda stable. But after these 20-25 mins the server throws a StackOverflowException at the point where it deserializes the tcp-stream, especially when setting the Image property from the byte[]-array. I thoroughly searched for recursive or endless loops, and regarding the fact that it occurs after thousands of sucessfull intervals, i could hardly imagine that. public byte[] ImageBase { get { MemoryStream ms = new MemoryStream(); _screen.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); return ms.GetBuffer(); } set { if (_screen != null) _screen.Dispose(); //preventing well-known image memory leak MemoryStream ms = new MemoryStream(value); try { _screen = Image.FromStream(ms); //<< EXCEPTION THROWING HERE } catch (StackOverflowException ex) //thx to new CLR management this wont work anymore -.- { Console.WriteLine(ex.Message + Environment.NewLine + ex.StackTrace); } ms.Dispose(); ms = null; } } I hope that more code would be unnecessary, or it could get very complex... Please help, i have no clue at all anymore thx Chris

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• Scheme Infix to Postfix

  - by Cody

  Let me establish that this is part of a class assignment, so I'm definitely not looking for a complete code answer. Essentially we need to write a converter in Scheme that takes a list representing a mathematical equation in infix format and then output a list with the equation in postfix format. We've been provided with the algorithm to do so, simple enough. The issue is that there is a restriction against using any of the available imperative language features. I can't figure out how to do this in a purely functional manner. This is our fist introduction to functional programming in my program. I know I'm going to be using recursion to iterate over the list of items in the infix expression like such. (define (itp ifExpr) ( ; do some processing using cond statement (itp (cdr ifExpr)) )) I have all of the processing implemented (at least as best I can without knowing how to do the rest) but the algorithm I'm using to implement this requires that operators be pushed onto a stack and used later. My question is how do I implement a stack in this function that is available to all of the recursive calls as well?

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• Reordering arguments using recursion (pro, cons, alternatives)

  - by polygenelubricants

  I find that I often make a recursive call just to reorder arguments. For example, here's my solution for endOther from codingbat.com: Given two strings, return true if either of the strings appears at the very end of the other string, ignoring upper/lower case differences (in other words, the computation should not be "case sensitive"). Note: str.toLowerCase() returns the lowercase version of a string. public boolean endOther(String a, String b) { return a.length() < b.length() ? endOther(b, a) : a.toLowerCase().endsWith(b.toLowerCase()); } I'm very comfortable with recursions, but I can certainly understand why some perhaps would object to it. There are two obvious alternatives to this recursion technique: Swap a and b traditionally public boolean endOther(String a, String b) { if (a.length() < b.length()) { String t = a; a = b; b = t; } return a.toLowerCase().endsWith(b.toLowerCase()); } Not convenient in a language like Java that doesn't pass by reference Lots of code just to do a simple operation An extra if statement breaks the "flow" Repeat code public boolean endOther(String a, String b) { return (a.length() < b.length()) ? b.toLowerCase().endsWith(a.toLowerCase()) : a.toLowerCase().endsWith(b.toLowerCase()); } Explicit symmetry may be a nice thing (or not?) Bad idea unless the repeated code is very simple ...though in this case you can get rid of the ternary and just || the two expressions So my questions are: Is there a name for these 3 techniques? (Are there more?) Is there a name for what they achieve? (e.g. "parameter normalization", perhaps?) Are there official recommendations on which technique to use (when)? What are other pros/cons that I may have missed?

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• Maintain one to one mapping between objects

  - by Rohan West

  Hi there, i have the following two classes that provide a one to one mapping between each other. How do i handle null values, when i run the second test i get a stackoverflow exception. How can i stop this recursive cycle? Thanks [TestMethod] public void SetY() { var x = new X(); var y = new Y(); x.Y = y; Assert.AreSame(x.Y, y); Assert.AreSame(y.X, x); } [TestMethod] public void SetYToNull() { var x = new X(); var y = new Y(); x.Y = y; y.X = null; Assert.IsNull(x.Y); Assert.IsNull(y.X); } public class X { private Y _y; public Y Y { get { return _y; } set { if(_y != value) { if(_y != null) { _y.X = null; } _y = value; if(_y != null) { _y.X = this; } } } } } public class Y { private X _x; public X X { get { return _x; } set { if (_x != value) { if (_x != null) { _x.Y = null; } _x = value; if (_x != null) { _x.Y = this; } } } } }

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• How to use Common Table Expression and check no duplication in sqlserver

  - by vodkhang

  I have a table references to itself. User table: id, username, managerid and managerid links back to id Now, I want to get all the managers including direct manager, manager of direct manager, so on and so forth... The problem is that I do not want to have a unstop recursive sql. So, I want to check if an id alreay in a list, I will not include it anymore. Here is my sql for that: with --the relation for all the subparts of ozsolar including itself all_managers (id, username, managerid, idlist) as ( --seed that is the ozsola part select u1.id, u1.username, u1.managerid, ' ' from users u1, users u2 where u1.id = u2.managerid and u2.id = 6 UNION ALL select u.id, u.username, u.managerid, idlist + ' ' + u.id from all_managers a, users u where a.managerid = u.id and charindex(cast(u.id as nvarchar(5)), idlist) != 0 ) --select the total number of subparts and group by subpart select id, username from all_managers; The problem is that in this line: select u1.id, u1.username, u1.managerid, ' ' The sqlserver complains with me that I can not put ' ' as the initialized for idlist. nvarchar(40) does not work as well. I do not know how to declare it inside a common table expression like this one. Usually, in db2, I can just put varchar(40)

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• Can I copy/clone a function in JavaScript?

  - by Craig Stuntz

  I'm using jQuery with the validators plugin. I would like to replace the "required" validator with one of my own. This is easy: jQuery.validator.addMethod("required", function(value, element, param) { return myRequired(value, element, param); }, jQuery.validator.messages.required); So far, so good. This works just fine. But what I really want to do is call my function in some cases, and the default validator for the rest. Unfortunately, this turns out to be recursive: jQuery.validator.addMethod("required", function(value, element, param) { // handle comboboxes with empty guids if (someTest(element)) { return myRequired(value, element, param); } return jQuery.validator.methods.required(value, element, param); }, jQuery.validator.messages.required); I looked at the source code for the validators, and the default implementation of "required" is defined as an anonymous method at jQuery.validator.messages.required. So there is no other (non-anonymous) reference to the function that I can use. Storing a reference to the function externally before calling addMethod and calling the default validator via that reference makes no difference. What I really need to do is to be able to copy the default required validator function by value instead of by reference. But after quite a bit of searching, I can't figure out how to do that. Is it possible? If it's impossible, then I can copy the source for the original function. But that creates a maintenance problem, and I would rather not do that unless there is no "better way."

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• dynamic ul with sub-levels

  - by Y.G.J

  i have this recursive code <ul> <% sql="SELECT * FROM cats ORDER BY orderid " rs.Open sql,Conn dim recArray If Not rs.EOF Then recArray = rs.getRows() dim i for i=0 to uBound(recArray,2) if recArray(1,i)=0 then call showMessage(i) end if next End If function showMessage(index) %><li><%=recArray(2,index)%></li><% for a=0 to uBound(recArray,2) if recArray(1,a) = recArray(0,index) Then %><ul><% call showMessage(a) %></ul><% end if next %></li><% end function %> </ul> inside the loop in the function i have the for the sub(s) but after each line of li it will close the ul how can i have that dynamic and to have the output like this <ul> <li></li> <li></li> <li> <ul> <li></li> <li></li> <li></li> </ul> </li> <li></li> </ul> and not like this <ul> <li></li> <li></li> <li> <ul><li></li></ul> <ul><li></li></ul> <ul><li></li></ul> </li> <li></li> </ul>

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• What is the right way to make a new XMLHttpRequest from an RJS response in Ruby on Rails?

  - by Yuri Baranov

  I'm trying to come closer to a solution for the problem of my previous question. The scheme I would like to try is following: User requests an action from RoR controller. Action makes some database queries, makes some calculations, sets some session variable(s) and returns some RJS code as the response. This code could either update a progress bar and make another ajax request. display the final result (e.g. a chart grahic) if all the processing is finished The browser evaluates the javascript representation of the RJS. It may make another (recursive? Is recursion allowed at all?) request, or just display the result for the user. So, my question this time is: how can I embed a XMLHttpRequest call into rjs code properly? Some things I'd like to know are: Should I create a new thread to avoid stack overflow. What rails helpers (if any) should I use? Have anybody ever done something similar before on Rails or with other frameworks? Is my idea sane?

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• process of connecting RTP with SIP via SDP & land lines

  - by TacB0sS

  Hello to everyone, I have a problem with starting a media session and to combine it with my SIP client. I've designed a recursive SIP client that reuse the same request template to send the next requests to server, according to the acceptable sequences noted in the RFC's, and examples that I read. as far as I could tell the SIP part is working fine registers to server invites, and authenticates. I didn't complete any calls to clients yet because of the content header needs to be filled up (which I didn't yet so I get a 503 from the server which is OK I guess). for a long time I didn't know where to start with the media session, and slowly learned how to use the JMF and I've constructed an object that handles RTP transmitting, now I'm standing at the cross road, on the one hand I have my SIP signaling but it needs the SDP content header to complete the invite, and on the other I have the RTP which is knows how to p2p. For me to complete my design I require your help with the following questions: Is there an easy//a simple//an implemented way to convert the Audio/Video format from the JMF into SDP media headers? or even a generator that I would input all the parameters for the content header, and it would generate a content header fast, or do I have to implement this myself? Once I've finished constructing the SDK and the SIP is up and running and I get an OK response from the server (after ringing and all), how do I start the media session? do I connect p2p according to caller details I send in the SIP invite? If 2 is correct, then how does a connection to land lines would be? does land lines knows that once they send an OK back to server they listen/start RTP session on a specific port? Or did I get everything wrong? :-/ I really appreciate any help I could I get, I looked every where for answers but they are not clear, they ignore question 2 as if it was an obvious thing, but for me it just isn't. Thank in advance, Adam Zehavi.

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• PyGTK/GIO: monitor directory for changes recursively

  - by detly

  Take the following demo code (from the GIO answer to this question), which uses a GIO FileMonitor to monitor a directory for changes: import gio def directory_changed(monitor, file1, file2, evt_type): print "Changed:", file1, file2, evt_type gfile = gio.File(".") monitor = gfile.monitor_directory(gio.FILE_MONITOR_NONE, None) monitor.connect("changed", directory_changed) import glib ml = glib.MainLoop() ml.run() After running this code, I can then create and modify child nodes and be notified of the changes. However, this only works for immediate children (I am aware that the docs don't say otherwise). The last of the following shell commands will not result in a notification: touch one mkdir two touch two/three Is there an easy way to make it recursive? I'd rather not manually code something that looks for directory creation and adds a monitor, removing them on deletion, etc. The intended use is for a VCS file browser extension, to be able to cache the statuses of files in a working copy and update them individually on changes. So there might by anywhere from tens to thousands (or more) directories to monitor. I'd like to just find the root of the working copy and add the file monitor there. I know about pyinotify, but I'm avoiding it so that this works under non-Linux kernels such as FreeBSD or... others. As far as I'm aware, the GIO FileMonitor uses inotify underneath where available, and I can understand not emphasising the implementation to maintain some degree of abstraction, but it suggested to me that it should be possible. (In case it matters, I originally posted this on the PyGTK mailing list.)

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• I want to find the span tag beween the LI tag and its attributes but no luck.

  - by Mahesh

  I want to find the span tag beween the LI tag and its attributes. Trying with beautful soap but no luck. Details of my code. Is any one point me right methodlogy In this this code, my getId function should return me id = "0_False-2" Any one know right method? from BeautifulSoup import BeautifulSoup as bs import re html = '<ul>\ <li class="line">&nbsp;</li>\ <li class="folder-open-last" id="0">\ <img style="float: left;" class="trigger" src="/media/images/spacer.gif" border="0">\ <span class="text" id="0_False">NOC</span><ul style="display: block;"><li class="line">&nbsp;</li><li class="doc" id="1"><span class="active text" id="0_False-1">PNQAIPMS1</span></li><li class="line">&nbsp;</li><li class="doc-last" id="2"><span class="text" id="0_False-2">PNQAIPMS2</span></li><li class="line-last"></li></ul></li><li class="line-last"></li>\ </ul>' def getId(html, txt): soup = bs(html) soup.findAll('ul',recursive=False) head = soup.contents[0] temp = head elements = {} while True: # It temp is None that means no HTML tags are available if temp == None: break #print temp if re.search('li', str( temp)) != None: attr = str(temp.attrs).encode('ascii','ignore') attr = attr.replace(' ', '') attr = attr.replace('[', '') attr = attr.replace(']', '') attr = attr.replace(')', '') attr = attr.replace('(', '') attr = attr.replace('u\'', '') attr = attr.replace('\'', '') attr = attr.split(',') span = str(temp.text) if span == txt: return attr[3] temp = temp.next else: temp = temp.next id = getId(html,"PNQAIPMS2") print "ID = " + id

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• Serializing MDI Winforms for persistency

  - by Serge

  Hello, basically my project is an MDI Winform application where a user can customize the interface by adding various controls and changing the layout. I would like to be able to save the state of the application for each user. I have done quite a bit of searching and found these: http://stackoverflow.com/questions/2076259/how-to-auto-save-and-auto-load-all-properties-in-winforms-c http://stackoverflow.com/questions/1669522/c-save-winform-or-controls-to-file Basically from what I understand, the best approach is to serialize the data to XML, however winform controls are not serializable, so I would have use surrogate classes: http://www.codeproject.com/KB/dotnet/Surrogate_Serialization.aspx Now, do I need to write a surrogate class for each of my controls? I would need to write some sort of a recursive algorithm to save all my controls, what is the best approach to do accomplish that? How would I then restore all the windows, should I use the memento design pattern for that? If I want to implement multiple users later, should I use Nhibernate to store all the object data in a database? I am still trying to wrap my head around the problem and if anyone has any experience or advice I would greatly appreciate it, thanks.

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• Number Algorithm

  - by James

  I've been struggling to wrap my head around this for some reason. I have 15 bits that represent a number. The bits must match a pattern. The pattern is defined in the way the bits start out: they are in the most flush-right representation of that pattern. So say the pattern is 1 4 1. The bits will be: 000000010111101 So the general rule is, take each number in the pattern, create that many bits (1, 4 or 1 in this case) and then have at least one space separating them. So if it's 1 2 6 1 (it will be random): 001011011111101 Starting with the flush-right version, I want to generate every single possible number that meets that pattern. The # of bits will be stored in a variable. So for a simple case, assume it's 5 bits and the initial bit pattern is: 00101. I want to generate: 00101 01001 01010 10001 10010 10100 I'm trying to do this in Objective-C, but anything resembling C would be fine. I just can't seem to come up with a good recursive algorithm for this. It makes sense in the above example, but when I start getting into 12431 and having to keep track of everything it breaks down.

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• Generate number sequences with LINQ

  - by tanascius

  I try to write a LINQ statement which returns me all possible combinations of numbers (I need this for a test and I was inspired by this article of Eric Lippert). The method's prototype I call looks like: IEnumerable<Collection<int>> AllSequences( int start, int end, int size ); The rules are: all returned collections have a length of size number values within a collection have to increase every number between start and end should be used So calling the AllSequences( 1, 5, 3 ) should result in 10 collections, each of size 3: 1 2 3 1 2 4 1 2 5 1 3 4 1 3 5 1 4 5 2 3 4 2 3 5 2 4 5 3 4 5 Now, somehow I'd really like to see a pure LINQ solution. I am able to write a non LINQ solution on my own, so please put no effort into a solution without LINQ. My tries so far ended at a point where I have to join a number with the result of a recursive call of my method - something like: return from i in Enumerable.Range( start, end - size + 1 ) select BuildCollection(i, AllSequences( i, end, size -1)); But I can't manage it to implement BuildCollection() on a LINQ base - or even skip this method call. Can you help me here?

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• Why does my ActivePerl program report 'Sorry. Ran out of threads'?

  - by Zaid

  Tom Christiansen's example code (à la perlthrtut) is a recursive, threaded implementation of finding and printing all prime numbers between 3 and 1000. Below is a mildly adapted version of the script #!/usr/bin/perl # adapted from prime-pthread, courtesy of Tom Christiansen use strict; use warnings; use threads; use Thread::Queue; sub check_prime { my ($upstream,$cur_prime) = @_; my $child; my $downstream = Thread::Queue->new; while (my $num = $upstream->dequeue) { next unless ($num % $cur_prime); if ($child) { $downstream->enqueue($num); } else { $child = threads->create(\&check_prime, $downstream, $num); if ($child) { print "This is thread ",$child->tid,". Found prime: $num\n"; } else { warn "Sorry. Ran out of threads.\n"; last; } } } if ($child) { $downstream->enqueue(undef); $child->join; } } my $stream = Thread::Queue->new(3..shift,undef); check_prime($stream,2); When run on my machine (under ActiveState & Win32), the code was capable of spawning only 118 threads (last prime number found: 653) before terminating with a 'Sorry. Ran out of threads' warning. In trying to figure out why I was limited to the number of threads I could create, I replaced the use threads; line with use threads (stack_size => 1);. The resultant code happily dealt with churning out 2000+ threads. Can anyone explain this behavior?

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• Dynamically created operators

  - by Gero

  I created a program using dev-cpp and wxwidgets which solves a puzzle. The user must fill the operations blocks and the results blocks, and the program will solve it. Im solving it using bruteforce, i generate all non repeated 9 length number combinations using a recursive algorithm. It does it pretty fast. Up to here all is great! But the problem is when my program operates depending the character on the blocks. Its extremely slow (it never gets the answer), because of the chars comparation against +, -, *, etc. Im doing a CASE. Is there some way or some programming language wich allows dinamic creation of operators? So i can define the operator ROW1COL2 to be a +, and the same way to all other operations. I leave a screenshot of the app, so its easier to understand how the puzzle works. http://www.imageshare.web.id/images/9gg5cev8vyokp8rhlot9.png PD: The algorithm works, i tryed it with a trivial puzzle, and solved it in a second.

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• NSOutlineView/NSTreeController - calculate sum of column

  - by matei

  I have a NSOutlineView bound to a NSTreeController. My data items are a custom class , let's call them "Row", and suppose a Row contains a "name" and a numeric field called "number" . All these "Rows" are found in let's say a "RowContainer" which has a "rows" mutable array holding the parent (level 0) rows. Each row also has a "children" NSMutableArray member which holds it's children. I have this working, and I want to display under the outlineview a textfield with the sum of all the "number" values of the rows. I bound this textfield to a "total" property of the "RowContainer". Now the problem is how or from where to trigger the recalculation of the "total" property, since this involves a recursive walk on the tree of rows, and I always get a "Collection was mutated while being enumerated" error. I've tried making a method "recalculateTotal", and calling it from the "setNumber" method of the "Row" class , but same error occurs. If I put the recalculation logic in the "total" getter, I can't trigger it to do the math. I'm sure the solution is simple but I can't see it

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• Changing CSS Rules using JavaScript or jQuery

  - by Praveen Kumar

  Initial Research I am aware of using .css() to get and set the CSS rules of a particular element. I have seen a website with this CSS: body, table td, select { font-family: Arial Unicode MS, Arial, sans-serif; font-size: small; } I never liked Arial Unicode as a font. Well, that was my personal feel. So, I would use Chrome's Style Inspector to edit the Arial Unicode MS to Segoe UI or something which I like. Is there anyway, other than using the following to achieve the same? Case I $("body, table td, select").css("font-family", "Segoe UI"); Recursive, performance intensive. Doesn't work when things are loaded on the fly. Case II $('<style>body, table td, select {font-famnily: "Segoe UI";}</style>') .appendTo("head"); Any other better method than this? Creates a lot of <style> tags!

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• Unexpected performance curve from CPython merge sort

  - by vkazanov

  I have implemented a naive merge sorting algorithm in Python. Algorithm and test code is below: import time import random import matplotlib.pyplot as plt import math from collections import deque def sort(unsorted): if len(unsorted) <= 1: return unsorted to_merge = deque(deque([elem]) for elem in unsorted) while len(to_merge) > 1: left = to_merge.popleft() right = to_merge.popleft() to_merge.append(merge(left, right)) return to_merge.pop() def merge(left, right): result = deque() while left or right: if left and right: elem = left.popleft() if left[0] > right[0] else right.popleft() elif not left and right: elem = right.popleft() elif not right and left: elem = left.popleft() result.append(elem) return result LOOP_COUNT = 100 START_N = 1 END_N = 1000 def test(fun, test_data): start = time.clock() for _ in xrange(LOOP_COUNT): fun(test_data) return time.clock() - start def run_test(): timings, elem_nums = [], [] test_data = random.sample(xrange(100000), END_N) for i in xrange(START_N, END_N): loop_test_data = test_data[:i] elapsed = test(sort, loop_test_data) timings.append(elapsed) elem_nums.append(len(loop_test_data)) print "%f s --- %d elems" % (elapsed, len(loop_test_data)) plt.plot(elem_nums, timings) plt.show() run_test() As much as I can see everything is OK and I should get a nice N*logN curve as a result. But the picture differs a bit: Things I've tried to investigate the issue: PyPy. The curve is ok. Disabled the GC using the gc module. Wrong guess. Debug output showed that it doesn't even run until the end of the test. Memory profiling using meliae - nothing special or suspicious. ` I had another implementation (a recursive one using the same merge function), it acts the similar way. The more full test cycles I create - the more "jumps" there are in the curve. So how can this behaviour be explained and - hopefully - fixed? UPD: changed lists to collections.deque UPD2: added the full test code UPD3: I use Python 2.7.1 on a Ubuntu 11.04 OS, using a quad-core 2Hz notebook. I tried to turn of most of all other processes: the number of spikes went down but at least one of them was still there.

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• Swing: what to do when a JTree update takes too long and freezes other GUI elements?

  - by java.is.for.desktop

  Hello, everyone! I know that GUI code in Java Swing must be put inside SwingUtilities.invokeAndWait or SwingUtilities.invokeLater. This way threading works fine. Sadly, in my situation, the GUI update it that thing which takes much longer than background thread(s). More specific: I update a JTree with about just 400 entries, nesting depth is maximum 4, so should be nothing scary, right? But it takes sometimes one second! I need to ensure that the user is able to type in a JTextPane without delays. Well, guess what, the slow JTree updates do cause delays for JTextPane during input. It refreshes only as soon as the tree gets updated. I am using Netbeans and know empirically that a Java app can update lots of information without freezing the rest of the UI. How can it be done? NOTE 1: All those DefaultMutableTreeNodes are prepared outside the invokeAndWait. NOTE 2: When I replace invokeAndWait with invokeLater the tree doesn't get updated. NOTE 3: Fond out that recursive tree expansion takes far the most time. NOTE 4: I'm using custom tree cell renderer, will try without and report. NOTE 4a: My tree cell renderer uses a map to cache and reuse created JTextComponents, depending on tree node (as a key). CLUE 1: Wow! Without setting custom cell renderer it's 10 times faster. I think, I'll need few good tutorials on writing custom tree cell renderers.

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• Java: how to get all subdirs recursively?

  - by HH

  Before debugging the late-hour-out-of-bound-recursive-function: is there a command to get subdirs? giveMeSubDirs(downToPath)? // WARNING: RECURSION out of bound public HashSet<FileObject> getAllDirs(String path) { HashSet<FileObject> checkedDirs = new HashSet<FileObject>(); HashSet<FileObject> allDirs = new HashSet<FileObject>(); String startingPath = path; File fileThing = new File(path); FileObject fileObject = new FileObject(fileThing); for (FileObject dir : getDirsInDir(path)) { // SUBDIR while ( !checkedDirs.contains(dir) && !(getDirsInDir(dir.getFile().getParent()).size() == 0)) { // DO NOT CHECK TOP DIRS if any bottom dir UNCHECKED! while ( uncheckedDirsOnLevel(path, checkedDirs).size() > 0) { while (getDirsInDir(path).size() == 0 || (numberOfCheckedDirsOnLevel(path, checkedDirs)==getDirsInDir(path).size())) { allDirs.add(new FileObject(new File(path))); checkedDirs.add(new FileObject(new File(path))); if(traverseDownOneLevel(path) == startingPath ) return allDirs; //get nearer to the root path = traverseDownOneLevel(path); } path = giveAnUncheckedDir(path, checkedDirs); if ( path == "NoUnchecked.") { checkedDirs.add(new FileObject( (new File(path)).getParentFile() )); break; } } } } return allDirs; }

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• Database design for a media server containing movies, music, tv and everything in between?

  - by user364114

  In the near future I am attempting to design a media server as a personal project. MY first consideration to get the project underway is architecture, it will certainly be web based but more specifically than that I am looking for suggestions on the database design. So far I am considering something like the following, where I am using [] to represent a table, the first text is the table name to give an idea of purpose and the items within {} would be fields of the table. Also not, fid is functional id referencing some other table. [Item {id, value/name, description, link, type}] - this could be any entity, single song or whole music album, game, movie - almost see this as a recursive relation, ie. a song is an item but an album that song is part of is also an item or for example a tv season is an item, with multiple items being tv episodes [Type {id, fid, mime type, etc}] - file type specific information - could identify how code handles streaming/sending this item to a user [Location {id, fid, path to file?}] [Users {id, username, email, password, ...? }] - user account information [UAC {id, fid, acess level}] - i almost feel its more flexible to seperate access control permissions form the user accounts themselves [ItemLog {id, fid, fid2, timestamp}] - fid for user id, and fid2 for item id - this way we know what user access what when [UserLog {id, fid, timestamp}] -both are logs for access, whether login or last item access [Quota {id, fid, cap}] - some sort of way to throttle users from queing up the entire site and letting it download ... Suggestions or comments are welcome as the hope is that this project will be a open source project once some code is laid out.

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• CakePHP - hasMany not fetching?

  - by Paolo Bergantino

  Maybe I am just having a slow day, but for the life of me I can't figure out why this is happening. I haven't done CakePHP in a while and I am trying to use the 1.3 version, but this doesn't seem to be working... I have two models: area.php <?php class Area extends AppModel { var $name = 'Area'; var $useTable = 'OR_AREA'; var $primaryKey = 'A_ID'; var $belongsTo = array( 'Building' => array( 'className' => 'Building', 'foreignKey' => 'FK_B_ID', ), 'Facility' => array( 'className' => 'Facility', 'foreignKey' => 'FK_F_ID', ), 'System' => array( 'className' => 'System', 'foreignKey' => 'FK_S_ID', ) ); } ?> building.php <?php class Building extends AppModel { var $name = 'Building'; var $useTable = 'OR_BLDG'; var $primaryKey = 'B_ID'; var $hasMany = array( 'Area' => array( 'className' => 'Area', 'foreignKey' => 'FK_B_ID', ) ); } ?> OR_AREA has a column titled FK_B_ID that refers to the B_ID. If I run something like: $this->Building->find('all', array('recursive' => 2)); I get empty [Area] arrays for all the Buildings even though there are plenty of Areas in the OR_AREA table that are associated to buildings. Not only that, the Query Table doesn't even show CakePHP attempted to find anything but all the records in OR_BLDG. All the more puzzling, if I do: $this->Area->find('all'); I get all the Areas and the [Building] arrays are populated when appropriate. What am I missing?

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