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  • How to detect column conflicts with Hibernate?

    - by Slim
    So let's say I have an ArrayList full of Products that need to be committed to the database via Hibernate. There are already a large number of Products in the database. Each product has an ID. Note this is NOT the PK that is autogenerated by Hibernate. My questions is: what is the best way to detect conflicts with this ID? I am looking for a relatively efficient method of obtaining, from the the database, a List of Products that share an ID with any of the Products in my ArrayList. This is all in a single table called Products and the ID attribute is in column ProductID. The way I've done it is grabbing a list of all Products in the database, and compared each one with each entry in my ArrayList - but that is seriously inefficient and I don't think it would work well with a larger database. How should it be done? Thanks. I say "relatively" efficient because efficiency is not the primary concern, but it shouldn't take noticeably long to test against a table of ~1000-5000 rows. Help? EDIT* I'm very new to hibernate and below is the best I've come up with. How does this look? for(long id : idList){ //idList just holds the IDs of each Product in my ArrayList Query query = session.createQuery("select product from Product product where product.id = :id"); query.setLong("id", id); for(int i = 0; i < query.list().size(); i++){ listOfConflictingProducts.add((Product) query.list().get(i)); } }

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  • Passing a WHERE clause for a Linq-to-Sql query as a parameter

    - by Mantorok
    Hi all This is probably pushing the boundaries of Linq-to-Sql a bit but given how versatile it has been so far I thought I'd ask. I have 3 queries that are selecting identical information and only differ in the where clause, now I know I can pass a delegate in but this only allows me to filter the results already returned, but I want to build up the query via parameter to ensure efficiency. Here is the query: from row in DataContext.PublishedEvents join link in DataContext.PublishedEvent_EventDateTimes on row.guid equals link.container join time in DataContext.EventDateTimes on link.item equals time.guid where row.ApprovalStatus == "Approved" && row.EventType == "Event" && time.StartDate <= DateTime.Now.Date.AddDays(1) && (!time.EndDate.HasValue || time.EndDate.Value >= DateTime.Now.Date.AddDays(1)) orderby time.StartDate select new EventDetails { Title = row.EventName, Description = TrimDescription(row.Description) }; The code I want to apply via a parameter would be: time.StartDate <= DateTime.Now.Date.AddDays(1) && (!time.EndDate.HasValue || time.EndDate.Value >= DateTime.Now.Date.AddDays(1)) Is this possible? I don't think it is but thought I'd check out first. Thanks

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  • Preprocessor "macro function" vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • Getting problem in threading in JAVA

    - by chetans
    In this program i want to stop GenerateImage & MovingImage Thread both... And i want to start those threads from begining. Can u send me the solution? Here is the code........ package Game; import java.applet.Applet; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Image; import java.awt.MediaTracker; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import java.net.MalformedURLException; import java.net.URL; public class ThreadInApplet extends Applet implements KeyListener { private static final long serialVersionUID = 1L; Image[] asteroidImage; Image spaceshipImage; String levelstr="Easy Level"; int[] XPos,YPos; int number=0,XPosOfSpaceship,YPosOfSpaceship,NoOfObstacles=5,speed=1,level=1,spaceBtnPressdCntr=0; boolean gameStart=false,pauseGame=false,collideUp=false,collideDown=false,collideLeft=false,collideRight=false; private Image offScreenImage; private Dimension offScreenSize; private Graphics offScreenGraphics; Thread GenerateImages,MoveImages; public void init() { try { GenerateImages=new Thread () //thread to create obstacles { synchronized public void run () { for(int g=0;g<NoOfObstacles;g++) { try { sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } number++; // Temporary counter to count the no of obstacles created } } } ; MoveImages=new Thread () //thread to move obstacles { @SuppressWarnings("deprecation") synchronized public void run () { while(YPos[NoOfObstacles-1]!=600) { pauseGame=false; if(collide()==true) { GenerateImages.suspend(); repaint(); } else GenerateImages.resume(); for(int l=0;l<number;l++) { if(collide()==false) YPos[l]++; else GenerateImages.suspend(); } repaint(); try { sleep(speed); } catch (InterruptedException e) { e.printStackTrace(); } } if(YPos[NoOfObstacles-1]>=600) //level complete state { level++; try { levelUpdation(level); System.out.println("aahe"); } catch (MalformedURLException e) { e.printStackTrace(); } repaint(); } } }; initialPos(); spaceshipImage=getImage(new URL(getCodeBase(),"images/space.png")); for(int i=0;i<NoOfObstacles;i++) { asteroidImage[i]=getImage(new URL(getCodeBase(),"images/asteroid.png")); XPos[i]=(int) (Math.random()*700); YPos[i]=0; } MediaTracker tracker = new MediaTracker (this); for(int i=0;i<NoOfObstacles;i++) { tracker.addImage (asteroidImage[i], 0); } } catch (MalformedURLException e) { e.printStackTrace(); } setBackground(Color.black); addKeyListener(this); } //Sets initial positions of spaceship & obstacle images------------------------------------------------------ public void initialPos() throws MalformedURLException { asteroidImage=new Image[NoOfObstacles]; XPos=new int[NoOfObstacles]; YPos=new int[NoOfObstacles]; XPosOfSpaceship=getWidth()/2-35; YPosOfSpaceship=getHeight()-100; collideUp = false; collideDown=false; collideLeft=false; collideRight=false; } //level finished updations------------------------------------------------------------------------------ @SuppressWarnings("deprecation") public void levelUpdation(int level) throws MalformedURLException { NoOfObstacles=NoOfObstacles+20; speed=speed-3; System.out.println(NoOfObstacles+" "+speed); pauseGame=true; initialPos(); repaint(); } //paint method of graphics to print the messages--------------------------------------------------------- public void paint(Graphics g) { g.setColor(Color.white); if(gameStart==false) { g.drawString("SPACE to start", (getWidth()/2)-15, getHeight()/2); g.drawString(levelstr, (getWidth()/2), getHeight()/2+20); } if(level>1) { if(level==2) levelstr="Medium Level"; else levelstr="High Level"; g.drawString("Level Complete ", (getWidth()/2)-15, getHeight()/2); g.drawString(levelstr, (getWidth()/2), getHeight()/2+20); //g.drawString("SPACE to start", (getWidth()/2)-15, getHeight()/2+40); } for(int n=0;n<number;n++) { if(n>0) g.drawImage(asteroidImage[n],XPos[n],YPos[n],this); } g.drawImage(spaceshipImage,XPosOfSpaceship,YPosOfSpaceship,this); } //update method of graphics to print the messages--------------------------------------------------------- @SuppressWarnings("deprecation") public void update(Graphics g) { Dimension d = size(); if((offScreenImage == null) || (d.width != offScreenSize.width) || (d.height != offScreenSize.height)) { offScreenImage = createImage(d.width, d.height); offScreenSize = d; offScreenGraphics = offScreenImage.getGraphics(); } offScreenGraphics.clearRect(0, 0, d.width, d.height); paint(offScreenGraphics); g.drawImage(offScreenImage, 0, 0, null); } public void keyReleased(KeyEvent arg0){} public void keyTyped(KeyEvent arg0) {} //---------------------Key pressed event to start game & to move the spaceship-------------------------------------- public void keyPressed(KeyEvent e) { if(e.getKeyCode()==32) { spaceBtnPressdCntr++; if(spaceBtnPressdCntr==1) { gameStart=true; GenerateImages.start(); MoveImages.start(); } } if(gameStart==true) { if(e.getKeyCode()==37) { new Thread () { @SuppressWarnings("deprecation") synchronized public void run () { for(int cnt1=1;cnt1<=10;cnt1++) { if(collide()==true && collideLeft == true) { GenerateImages.suspend(); } else { if(XPosOfSpaceship>0) XPosOfSpaceship--; } } repaint(); } }.start(); } if(e.getKeyCode()==38) { new Thread () { @SuppressWarnings("deprecation") synchronized public void run () { for(int cnt1=1;cnt1<=10;cnt1++) { if(collide()==true && collideUp == true) { GenerateImages.suspend(); } else { if(YPosOfSpaceship>10) YPosOfSpaceship--; } } repaint(); } }.start(); } if(e.getKeyCode()==39) { new Thread () { @SuppressWarnings("deprecation") synchronized public void run () { for(int cnt1=1;cnt1<=10;cnt1++) { if(collide()==true && collideRight == true) { GenerateImages.suspend(); } else { if(XPosOfSpaceship<750) XPosOfSpaceship++; } } repaint(); } }.start(); } if(e.getKeyCode()==40) { new Thread () { @SuppressWarnings("deprecation") synchronized public void run () { for(int cnt1=1;cnt1<=10;cnt1++) { if(collide()==true && collideDown == true) { GenerateImages.suspend(); } else { if(YPosOfSpaceship<550) YPosOfSpaceship++; } } repaint(); } }.start(); } } } //------------------------------Collision checking between Spaceship & obstacles------------------------------ public boolean collide() { int x1,y1,x2,y2,x3,y3,x4,y4; //coordinates of obstacles int a1,b1,a2,b2,a3,b3,a4,b4; //coordinates of spaceship a1 =XPosOfSpaceship; b1=YPosOfSpaceship; a2=a1+spaceshipImage.getWidth(this); b2=b1; a3=a1; b3=b1+spaceshipImage.getHeight(this); a4=a2; b4=b3; for(int a=0;a<number;a++) { x1 =XPos[a]; y1=YPos[a]; x2=x1+asteroidImage[a].getWidth(this); y2=y1; x3=x1; y3=y1+asteroidImage[a].getHeight(this); x4=x2; y4=y3; /********checking asteroid touch spaceship from up direction********/ if(y3==b1 && x4>=a1 && x4<=a2) { collideUp = true; collideDown=false; collideLeft=false; collideRight=false; return(true); } if(y3==b1 && x3>=a1 && x3<=a2) { collideUp = true; collideDown=false; collideLeft=false; collideRight=false; return(true); } /********checking asteroid touch spaceship from left direction******/ if(x2==a1 && y4>=b1 && y4<=b3) { collideLeft=true; collideUp = false; collideDown=false; collideRight=false; return(true); } if(x2==a1 && y2>=b1 && y2<=b3) { collideLeft=true; collideUp = false; collideDown=false; collideRight=false; return(true); } /********checking asteroid touch spaceship from right direction*****/ if(x1==a2 && y3>=b2 && y3<=b4) { collideRight=true; collideLeft=false; collideUp = false; collideDown=false; return(true); } if(x1==a2 && y1>=b2 && y1<=b4) { collideRight=true; collideLeft=false; collideUp = false; collideDown=false; return(true); } /********checking asteroid touch spaceship from down direction*****/ if(y1==b3 && x2>=a3 && x2<=a4) { collideDown=true; collideRight=false; collideLeft=false; collideUp = false; return(true); } if(y1==b3 && x1>=a3 && x1<=a4) { collideDown=true; collideRight=false; collideLeft=false; collideUp = false; return(true); } } return(false); } }

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  • IPad SQLite Push and Pull Data from external MS SQL Server DB

    - by MattyD
    This carries on from my previous post (http://stackoverflow.com/questions/4182664/ipad-app-pull-and-push-relational-data). My plan is that when the ipad application starts I am going to pull data (config data i.e. Departments, Types etc etc relational data that is used across the system) from a webhosted MS SQL Server DB via a webservice and populate it into an SQL Lite DB on the IPad. Then when I load a listing I will pull the data over the line again via a webservice and populate it into the SQL Lite db on the ipad (than just run select commands to populate the listing). My questions are: 1. What is the most efficient way to transfer data across the line via the web? Everyone seems to do it a different way. My idea is that I will have a webService for each type of data pull (e.g. RetrieveContactListing) that will query the db and than convert that data into "something" to send across the line. My question really is what is the "something" that it should be converting into? 2. Everyone talks about odata services. Is this suited for applications where complex read and writes are needed? Ive created a simple iphone app before that talked to an sql server db (i just sent my own structured xml across the line) but now with this app the data calls are going to be a lot larger so efficiency is key.

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  • Compact data structure for storing a large set of integral values

    - by Odrade
    I'm working on an application that needs to pass around large sets of Int32 values. The sets are expected to contain ~1,000,000-50,000,000 items, where each item is a database key in the range 0-50,000,000. I expect distribution of ids in any given set to be effectively random over this range. The operations I need on the set are dirt simple: Add a new value Iterate over all of the values. There is a serious concern about the memory usage of these sets, so I'm looking for a data structure that can store the ids more efficiently than a simple List<int>or HashSet<int>. I've looked at BitArray, but that can be wasteful depending on how sparse the ids are. I've also considered a bitwise trie, but I'm unsure how to calculate the space efficiency of that solution for the expected data. A Bloom Filter would be great, if only I could tolerate the false negatives. I would appreciate any suggestions of data structures suitable for this purpose. I'm interested in both out-of-the-box and custom solutions. EDIT: To answer your questions: No, the items don't need to be sorted By "pass around" I mean both pass between methods and serialize and send over the wire. I clearly should have mentioned this. There could be a decent number of these sets in memory at once (~100).

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  • Determining if an unordered vector<T> has all unique elements

    - by Hooked
    Profiling my cpu-bound code has suggested I that spend a long time checking to see if a container contains completely unique elements. Assuming that I have some large container of unsorted elements (with < and = defined), I have two ideas on how this might be done: The first using a set: template <class T> bool is_unique(vector<T> X) { set<T> Y(X.begin(), X.end()); return X.size() == Y.size(); } The second looping over the elements: template <class T> bool is_unique2(vector<T> X) { typename vector<T>::iterator i,j; for(i=X.begin();i!=X.end();++i) { for(j=i+1;j!=X.end();++j) { if(*i == *j) return 0; } } return 1; } I've tested them the best I can, and from what I can gather from reading the documentation about STL, the answer is (as usual), it depends. I think that in the first case, if all the elements are unique it is very quick, but if there is a large degeneracy the operation seems to take O(N^2) time. For the nested iterator approach the opposite seems to be true, it is lighting fast if X[0]==X[1] but takes (understandably) O(N^2) time if all the elements are unique. Is there a better way to do this, perhaps a STL algorithm built for this very purpose? If not, are there any suggestions eek out a bit more efficiency?

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  • Split UInt32 (audio frame) into two SInt16s (left and right)?

    - by morgancodes
    Total noob to anything lower-level than Java, diving into iPhone audio, and realing from all of the casting/pointers/raw memory access. I'm working with some example code wich reads a WAV file from disc and returns stereo samples as single UInt32 values. If I understand correctly, this is just a convenient way to return the 32 bits of memory required to create two 16 bit samples. Eventually this data gets written to a buffer, and an audio unit picks it up down the road. Even though the data is written in UInt32-sized chunks, it eventually is interpreted as pairs of 16-bit samples. What I need help with is splitting these UInt32 frames into left and right samples. I'm assuming I'll want to convert each UInt32 into an SInt16, since an audio sample is a signed value. It seems to me that for efficiency's sake, I ought to be able to simply point to the same blocks in memory, and avoid any copying. So, in pseudo-code, it would be something like this: UInt32 myStereoFrame = getFramefromFilePlayer; SInt16* leftChannel = getFirst16Bits(myStereoFrame); SInt16* rightChannel = getSecond16Bits(myStereoFrame); Can anyone help me turn my pseudo into real code?

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  • What are the general strategies for the server of an FPS multiplayer game to update its clients?

    - by Hooray Im Helping
    A friend and I were having a discussion about how a FPS server updates the clients connected to it. We watched a video of a guy cheating in Battlefield: Bad Company 2 and saw how it highlighted the position of enemies on the screen and it got us thinking. His contention was that the server only updates the client with information that is immediately relevant to the client. I.e. the server won't send information about enemy players if they are too far away from the client or out of the client's line of sight for reasons of efficiency. He was unsure though - he brought up the example of someone hiding behind a rock, not able to see anyone. If the player were suddenly to pop up where he had three players in his line of sight, there would be a 50ms delay before they were rendered on his screen while the server transmitted the necessary information. My contention was the opposite: that the server sends the client all the information about every player and lets the client sort out what is allowed and what isn't. I figured it would actually be less expensive computationally for the server to just send everything to the client and let the client do the heavy lifting, so to speak. I also figured this is how cheat programs work - they intercept the server packets, get the location of enemies, then show them on the client's view. So the question: What are some general policies or strategies a modern first person shooter server employs to keep its clients updated?

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  • Efficient Multiplication of Varying-Length #s [Conceptual]

    - by Milan Patel
    Write the pseudocode of an algorithm that takes in two arbitrary length numbers (provided as strings), and computes the product of these numbers. Use an efficient procedure for multiplication of large numbers of arbitrary length. Analyze the efficiency of your algorithm. I decided to take the (semi) easy way out and use the Russian Peasant Algorithm. It works like this: a * b = a/2 * 2b if a is even a * b = (a-1)/2 * 2b + a if a is odd My pseudocode is: rpa(x, y){ if x is 1 return y if x is even return rpa(x/2, 2y) if x is odd return rpa((x-1)/2, 2y) + y } I have 3 questions: Is this efficient for arbitrary length numbers? I implemented it in C and tried varying length numbers. The run-time in was near-instant in all cases so it's hard to tell empirically... Can I apply the Master's Theorem to understand the complexity...? a = # subproblems in recursion = 1 (max 1 recursive call across all states) n / b = size of each subproblem = n / 1 - b = 1 (problem doesn't change size...?) f(n^d) = work done outside recursive calls = 1 - d = 0 (the addition when a is odd) a = 1, b^d = 1, a = b^d - complexity is in n^d*log(n) = log(n) this makes sense logically since we are halving the problem at each step, right? What might my professor mean by providing arbitrary length numbers "as strings". Why do that? Many thanks in advance

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  • How should I link two items with MouseMovementListeners?

    - by user1708810
    I'm working on a program that will display two "views" of the same set of items. So I need to have something set up so that when the top down view is changed, the side view is updated (and vice versa). Here's a brief outline of the relevant code so you can get an idea of my structure so far: public class DraggableComponent extends JComponent { //Contains code for MouseMovementListener that makes the item draggable } public class ItemGraphic extends DraggableComponent { //Code to render the graphic } public class Item { private ItemGraphic topGraphic; private ItemGraphic sideGraphic; } I'm able to get each graphic to display fine in my GUI. I can also independently drag each graphic. I'm missing the "linking." Some ideas I've been thinking about: Have one listener for the whole GUI. Loop through each Item and if the cursor is within the bounds of either graphic, move the other graphic. I'm concerned about the efficiency of this method. Multiple "paired" listeners (not quite sure how this would work, but the idea is that each graphic would have a listener for the other paired graphic)

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  • Best (Java) book for understanding 'under the bonnet' for programming?

    - by Ben
    What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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  • How do I efficiently locate key-value pairs in a multi-dimensional PHP array?

    - by Kyle Noland
    I have an array in PHP as a result of the following query to a Wordpress database: SELECT * FROM wp_postmeta WHERE post_id = :id I am returned a multidimensional array that looks like this: Array ( [0] => Array ( [meta_id] => 380 [post_id] => 72 [meta_key] => _edit_last [meta_value] => 1 ) ... etc. What is the best way to find a particular key-value pair in this array? For instance, how would I located the row where [meta_key] = event_name so that I can extract that same row's [meta_value] value into a PHP variable? I realize I could turn this into many individual MySQL queries. Does anyone have an opinion of the efficiency of doing 10 SQL queries in a row rather than searching the array 10 times? I would think since the array is in memory, that will be the fastest method to find the values I need. Alternatively, is there a better way to query the database from the beginning so that my result set is formatted in a way that is easier to search?

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  • lapply slower than for-loop when used for a BiomaRt query. Is that expected?

    - by ptocquin
    I would like to query a database using BiomaRt package. I have loci and want to retrieve some related information, let say description. I first try to use lapply but was surprise by the time needed for the task to be performed. I thus tried a more basic for-loop and get a faster result. Is that expected or is something wrong with my code or with my understanding of apply ? I read other posts dealing with *apply vs for-loop performance (Here, for example) and I was aware that improved performance should not be expected but I don't understand why performance here is actually lower. Here is a reproducible example. 1) Loading the library and selecting the database : library("biomaRt") athaliana <- useMart("plants_mart_14") athaliana <- useDataset("athaliana_eg_gene",mart=athaliana) 2) Querying the database : loci <- c("at1g01300", "at1g01800", "at1g01900", "at1g02335", "at1g02790", "at1g03220", "at1g03230", "at1g04040", "at1g04110", "at1g05240" ) I create a function for the use in lapply : foo <- function(loci) { getBM("description","tair_locus",loci,athaliana) } When I use this function on the first element : > system.time(foo(cwp_loci[1])) utilisateur système écoulé 0.020 0.004 1.599 When I use lapply to retrieve the data for all values : > system.time(lapply(loci, foo)) utilisateur système écoulé 0.220 0.000 16.376 I then created a new function, adding a for-loop : foo2 <- function(loci) { for (i in loci) { getBM("description","tair_locus",loci[i],athaliana) } } Here is the result : > system.time(foo2(loci)) utilisateur système écoulé 0.204 0.004 10.919 Of course, this will be applied to a big list of loci, so the best performing option is needed. I thank you for assistance. EDIT Following recommendation of @MartinMorgan Simply passing the vector loci to getBM greatly improves the query efficiency. Simpler is better. > system.time(lapply(loci, foo)) utilisateur système écoulé 0.236 0.024 110.512 > system.time(foo2(loci)) utilisateur système écoulé 0.208 0.040 116.099 > system.time(foo(loci)) utilisateur système écoulé 0.028 0.000 6.193

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  • Exceptions over remote methods

    - by Andrei Vajna II
    What are the best practices for exceptions over remote methods? I'm sure that you need to handle all exceptions at the level of a remote method implementation, because you need to log it on the server side. But what should you do afterwards? Should you wrap the exception in a RemoteException (java) and throw it to the client? This would mean that the client would have to import all exceptions that could be thrown. Would it be better to throw a new custom exception with fewer details? Because the client won't need to know all the details of what went wrong. What should you log on the client? I've even heard of using return codes(for efficiency maybe?) to tell the caller about what happened. The important thing to keep in mind, is that the client must be informed of what went wrong. A generic answer of "Something failed" or no notification at all is unacceptable. And what about runtime (unchecked) exceptions?

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  • Concept: Information Into Memory Location.

    - by Richeve S. Bebedor
    I am having troubles conceptualizing an algorithm to be used to transform any information or data into a specific appropriate and reasonable memory location in any data structure that I will be devising. To give you an idea, I have a JPanel object instance and I created another Container type object instance of any subtype (note this is in Java because I love this language), then I collected those instances into a data structure not specifically just for those instances but also applicable to any type of object. Now my procedure for fetching those data again is to extract the object specific features similar in category to all object in that data structure and transform it into a integer data memory location (specifically as much as possible) or any type of data that will pertain to this transformation. And I can already access that memory location without further sorting or applications of O(n) time complex algorithms (which I think preferable but I wanted to do my own way XD). The data structure is of any type either binary tree, linked list, arrays or sets (and the like XD). What is important is I don't need to have successive comparing and analysis of data just to locate information in big structures. To give you a technical idea, I have to an array DS that contains JLabel object instance with a specific name "HelloWorld". But array DS contains other types of object (in multitude). Now this JLabel object has a location in the array at index [124324] (which is if you do any type of searching algorithm just to arrive at that location is conceivably slow because added to it the data structure used was an array *note please disregard the efficiency of the data structure to be used I just want to explain to you my concept XD). Now I want to equate "HelloWorld" to 124324 by using a conceptually made function applicable to all data types. So that I can do a direct search by doing this DS[extractLocation("HelloWorld")] just to get that JLabel instance. I know this may sound crazy but I want to test my concept of non-sorting feature extracting search algorithm for any data structure wherein my main problem is how to transform information to be stored into memory location of where it was stored.

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  • Preprocessor #define vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • Determing if an unordered vector<T> has all unique elements

    - by Hooked
    Profiling my cpu-bound code has suggested I that spend a long time checking to see if a container contains completely unique elements. Assuming that I have some large container of unsorted elements (with < and = defined), I have two ideas on how this might be done: The first using a set: template <class T> bool is_unique(vector<T> X) { set<T> Y(X.begin(), X.end()); return X.size() == Y.size(); } The second looping over the elements: template <class T> bool is_unique2(vector<T> X) { typename vector<T>::iterator i,j; for(i=X.begin();i!=X.end();++i) { for(j=i+1;j!=X.end();++j) { if(*i == *j) return 0; } } return 1; } I've tested them the best I can, and from what I can gather from reading the documentation about STL, the answer is (as usual), it depends. I think that in the first case, if all the elements are unique it is very quick, but if there is a large degeneracy the operation seems to take O(N^2) time. For the nested iterator approach the opposite seems to be true, it is lighting fast if X[0]==X[1] but takes (understandably) O(N^2) time if all the elements are unique. Is there a better way to do this, perhaps a STL algorithm built for this very purpose? If not, are there any suggestions eek out a bit more efficiency?

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  • :include and table aliasing

    - by dondo
    I'm suffering from a variant of the problem described here: ActiveRecord assigns table aliases for association joins fairly unpredictably. The first association to a given table keeps the table name. Further joins with associations to that table use aliases including the association names in the path... but it is common for app developers not to know about [other] joins at coding time. In my case I'm being bitten by a toxic mix of has_many and :include. Many tables in my schema have a state column, and the has_many wants to specify conditions on that column: has_many :foo, :conditions => {:state => 1}. However, since the state column appears in many tables, I disambiguate by explicitly specifying the table name: has_many :foo, :conditions => "this_table.state = 1". This has worked fine until now, when for efficiency I want to add an :include to preload a fairly deep tree of data. This causes the table to be aliased inconsistently in different code paths. My reading of the tickets referenced above is that this problem is not and will not be fixed in Rails 2.x. However, I don't see any way to apply the suggested workaround (to specify the aliased table name explicitly in the query). I'm happy to specify the table alias explicitly in the has_many statement, but I don't see any way to do so. As such, the workaround doesn't appear applicable to this situation (nor, I presume, in many 'named_scope' scenarios). Is there a viable workaround?

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  • Creation of model in core data on the fly

    - by user1740045
    How can we create a model in core data on the fly? I.e getting the schema of database from somewhere and then creating a Core Data Object graph? *QuesTion:* Yes thats fine, agreed with all the advantages. But, can anybody can tell practically, what is the benefit of integrating Core Data into project instead of using SQL directly. 1.No need to write SQL boiler plate code [but need to learn Core Data Model (steep curve)] 2.WE can undo and redo changes [but practically who needs it] 3.we can migrate to another schema [that can be done by SQLite as well jus need to add another field into table] 4.For say aggregation on some field in table,in Core Data we need to loop through Core Data Objects whereas in SQLite we need to first write SQLite Boiler Plate Code and then the basic aggregation SQL query,which is easy to write,only length of code will increase...But in case of Core Data (need to learn a lot). So apart from reducing the length of Code,does it actually adds value to project? or in terms of Memory Efficiency,Performance,etc.. PS: If anybody has actualy worked on Core Data(Model Creation On the Fly) , if possible share and gve pointers..thanks!

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  • 'Certificate types are not available' When creating computer certificate?

    - by Anicho
    Environment Windows Server 2008 sp1 Xeon CPU E5430 @ 2.66 GHz 16.0 GB Ram 64-bit Operating System 1TB Disk Space Server Role: SQL Server Other Information: Joint to domain, Logged in user domain administrator Issue Steps that cause issue: Create a computer certificate using mmc snap-in 'certificates' by right clicking on 'Certificates' folder Under 'root\Personal' tree, and clicking All Tasks - Request New Certificate. Certificate Enrollment window appears, you verify you are connected to your network and you are logged onto the domain. Then Click Next, which leads to a window stating the issue: "Certificate types are not available" "You cannot request a certificate this time because no certificate types are available. If you need a certificate contact your administrator." Wanted Solution Create a certificate on this server, to implement SSL connection to MSSQL servers.

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  • what appropriate "Allocation Unit Size" for an exFAT SD card with ReadyBoost

    - by Revolter
    I've brought an 4GB SD card and I'm dedicating it for use by ReadyBoost (on Windows7) Im looking to get the most profit on performance, so i've formatted it with exFAT (as recommended by Microsoft) but I have some doubts to define what best .Allocation Unit Size* I should choose. Since I can't get how ReadyBoost/SD card exactly read/seek the data, can someone tell what make choosing an Allocation Unit Size in favor of another for this scheme ? Apparently, ReadyBoost is allocating all the free space in SD card as one huge file, so a big Allocation Unit Size is advised for fastest reading time. I'm not confusing with ordinary HDD's ?

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  • How to resolve "svn: Can't find a temporary directory: Internal error"?

    - by HorusKol
    I have already googled the message, and I have plenty of disk space available on the SVN server (it's about 4% usage of 150 GB). I have noticed that when I try echo $TMPDIR at the command prompt on the SVN server I get nothing. What is making this a little confusing is that I only get this message from one location when I do an svn diff (that I've tested so far) - this error is not coming up when I try from three other computers (one of which is testing against the exact same repository, the other two are different repositories on the same svn server). About the only difference I can see is that the broken working copy is connecting to the server by an IP address where all the others are using a server name (although this resolves over DNS to the same IP Address). I'm hoping that I don't have to scratch the broken working copy and checkout a new one - unfortunately, this is a legacy project and not all changes have been properly revisioned.

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  • TEMP_PART01 and C drive

    - by SmartLemon
    So we have a Samsung series 9 laptop and it has a 128 GB solid state drive, the problem we are having with it is that it has 4 partitions, one that's 100MB (who knows what for), one thats 40 GB (Primary Windows partition), 60 GB partition (TEMP_PART01) and a microsoft office one. The primary windows partition only has less than, 30 MB left, we want to increase this space, I know that I could just move everything to temp_part01 but we are not quite sure on it. What we are thinking of doing is deleting this partition all together and extending the windows volume. The problem is that the extra partition has 55.7 remaining out of 59.7 GB, which means there is something on it, but it shows up with nothing when we go into it, when we change the settings to show hidden files, but still nothing, I then used CMD to list all the files using dir d: and still no files. So would it be safe to delete it and extend the windows volume? Or what should I do? Here's a screen shot:

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  • Very large database, very small portion most being retrieved in real time

    - by mingyeow
    Hi folks, I have an interesting database problem. I have a DB that is 150GB in size. My memory buffer is 8GB. Most of my data is rarely being retrieved, or mainly being retrieved by backend processes. I would very much prefer to keep them around because some features require them. Some of it (namely some tables, and some identifiable parts of certain tables) are used very often in a user facing manner How can I make sure that the latter is always being kept in memory? (there is more than enough space for these) More info: We are on Ruby on rails. The database is MYSQL, our tables are stored using INNODB. We are sharding the data across 2 partitions. Because we are sharding it, we store most of our data using JSON blobs, while indexing only the primary keys

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