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• Poor LLVM JIT performance

  - by Paul J. Lucas

  I have a legacy C++ application that constructs a tree of C++ objects. I want to use LLVM to call class constructors to create said tree. The generated LLVM code is fairly straight-forward and looks repeated sequences of: ; ... %11 = getelementptr [11 x i8*]* %Value_array1, i64 0, i64 1 %12 = call i8* @T_string_M_new_A_2Pv(i8* %heap, i8* getelementptr inbounds ([10 x i8]* @0, i64 0, i64 0)) %13 = call i8* @T_QueryLoc_M_new_A_2Pv4i(i8* %heap, i8* %12, i32 1, i32 1, i32 4, i32 5) %14 = call i8* @T_GlobalEnvironment_M_getItemFactory_A_Pv(i8* %heap) %15 = call i8* @T_xs_integer_M_new_A_Pvl(i8* %heap, i64 2) %16 = call i8* @T_ItemFactory_M_createInteger_A_3Pv(i8* %heap, i8* %14, i8* %15) %17 = call i8* @T_SingletonIterator_M_new_A_4Pv(i8* %heap, i8* %2, i8* %13, i8* %16) store i8* %17, i8** %11, align 8 ; ... Where each T_ function is a C "thunk" that calls some C++ constructor, e.g.: void* T_string_M_new_A_2Pv( void *v_value ) { string *const value = static_cast<string*>( v_value ); return new string( value ); } The thunks are necessary, of course, because LLVM knows nothing about C++. The T_ functions are added to the ExecutionEngine in use via ExecutionEngine::addGlobalMapping(). When this code is JIT'd, the performance of the JIT'ing itself is very poor. I've generated a call-graph using kcachegrind. I don't understand all the numbers (and this PDF seems not to include commas where it should), but if you look at the left fork, the bottom two ovals, Schedule... is called 16K times and setHeightToAtLeas... is called 37K times. On the right fork, RAGreed... is called 35K times. Those are far too many calls to anything for what's mostly a simple sequence of call LLVM instructions. Something seems horribly wrong. Any ideas on how to improve the performance of the JIT'ing?

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• Why does adding Crossover to my Genetic Algorithm gives me worse results?

  - by MahlerFive

  I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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• How to run some code only once in view

  - by Freewind

  I have a partial view called '_comment.erb', and it may be called by parent many times(e.g. in a loop). The '_comment.erb' looks like: <script> function aaa() {} </script> <%= comment.content %> <%=link_to_function 'Do', 'aaa()' %> You can see if the '_comment.erb' be called many times, that the javascript function 'aaa' will be re-defined many times. I hope it can be define only once, but I don't want to move it to parent view. I hope there is a method, say 'run_once', and I can use it like this: <%= run_once do %> <script> function aaa() {} </script> <% end %> <%= comment.content %> <%=link_to_function 'Do', 'aaa()' %> No matter how many time I call the '_comment.erb', the code inside 'run_once' will be run only once. What shall I do?

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• Game of life in F# with accelerator

  - by jpalmer

  I'm trying to write life in F# using accelerator v2, but for some odd reason my output isn't square despite all my arrays being square - It appears that everything but a rectangular area in the top left of the matrix is being set to false. I've got no idea how this could be happening as all my operations should treat the entire array equally. Any ideas? open Microsoft.ParallelArrays open System.Windows.Forms open System.Drawing type IPA = IntParallelArray type BPA = BoolParallelArray type PAops = ParallelArrays let RNG = new System.Random() let size = 1024 let arrinit i = Array2D.init size size (fun x y -> i) let target = new DX9Target() let threearr = new IPA(arrinit 3) let twoarr = new IPA(arrinit 2) let onearr = new IPA(arrinit 1) let zeroarr = new IPA(arrinit 0) let shifts = [|-1;-1|]::[|-1;0|]::[|-1;1|]::[|0;-1|]::[|0;1|]::[|1;-1|]::[|1;0|]::[|1;1|]::[] let progress (arr:BPA) = let sums = shifts //adds up whether a neighbor is on or not |> List.fold (fun (state:IPA) t ->PAops.Add(PAops.Cond(PAops.Rotate(arr,t),onearr,zeroarr),state)) zeroarr PAops.Or(PAops.CompareEqual(sums,threearr),PAops.And(PAops.CompareEqual(sums,twoarr),arr)) //rule for life let initrandom () = Array2D.init size size (fun x y -> if RNG.NextDouble() > 0.5 then true else false) type meform () as self= inherit Form() let mutable array = new BoolParallelArray(initrandom()) let timer = new System.Timers.Timer(1.0) //redrawing timer do base.DoubleBuffered <- true do base.Size <- Size(size,size) do timer.Elapsed.Add(fun _ -> self.Invalidate()) do timer.Start() let draw (t:Graphics) = array <- array |> progress let bmap = new System.Drawing.Bitmap(size,size) target.ToArray2D array |> Array2D.iteri (fun x y t -> if not t then bmap.SetPixel(x,y,Color.Black)) t.DrawImageUnscaled(bmap,0,0) do self.Paint.Add(fun t -> draw t.Graphics) do Application.Run(new meform())

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• jquery .submit live click runs more than once

  - by fxuser

  I use the following code to run my form ajax requests but when i use the live selector on a button i can see the ajax response fire 1 time, then if i re-try it 2 times, 3 times, 4 times and so on... I use .live because i also have a feature to add a post and that appears instantly so the user can remove it without refreshing the page... Then this leads to the above problem... using .click could solve this but it's not the ideal solution i'm looking for... jQuery.fn.postAjax = function(success_callback, show_confirm) { this.submit(function(e) { e.preventDefault(); if (show_confirm == true) { if (confirm('Are you sure you want to delete this item? You can\'t undo this.')) { $.post(this.action, $(this).serialize(), $.proxy(success_callback, this)); } } else { $.post(this.action, $(this).serialize(), $.proxy(success_callback, this)); } return false; }) return this; }; $(document).ready(function() { $(".delete_button").live('click', function() { $(this).parent().postAjax(function(data) { if (data.error == true) { } else { } }, true); }); });? EDIT: temporary solution is to change this.submit(function(e) { to this.unbind('submit').bind('submit',function(e) { the problem is how can i protect it for real because people who know how to use Firebug or the same tool on other browsers can easily alter my Javascript code and re-create the problem

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• What does O(log n) mean exactly?

  - by Andreas Grech

  I am currently learning about Big O Notation running times and amortized times. I understand the notion of O(n) linear time, meaning that the size of the input affects the growth of the algorithm proportionally...and the same goes for, for example, quadratic time O(n2) etc..even algorithms, such as permutation generators, with O(n!) times, that grow by factorials. For example, the following function is O(n) because the algorithm grows in proportion to its input n: f(int n) { int i; for (i = 0; i < n; ++i) printf("%d", i); } Similarly, if there was a nested loop, the time would be O(n2). But what exactly is O(log n)? For example, what does it mean to say that the height of a complete binary tree is O(log n)? I do know (maybe not in great detail) what Logarithm is, in the sense that: log10 100 = 2, but I cannot understand how to identify a function with a logarithmic time.

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• Web application date time localization best practice at 201x

  - by Hieu Lam

  Hi all, I have worked for various web projects but correct date time localization have not been done and considered throroughly so I want to ask this very typical problem here and I want to hear comments from expert in this problem What is the correct strategy for storing a date/time value from client from server As I understand, because of locale and timezone so we have to do the conversion, I have heard about GMT or UTC time and after do some search it seems that UTC is more accurate ? so we will convert from client time - UTC+0 when saving and when we read the value from server to client, we convert from server time back to client time again ? However, I see in some website, at the bottom have the sentence "All times are in UTC", "All times are in GMT" and also "All times are in your local time". So maybe not all the sites do the convertion back and forth ? And in that case the user has to manually do the date/time conversion ? How to display the date/time convenient to user based on his locale and region How to provide personalization on date/time value ? I had one time depends on vbscript to do the display and the format is read from windows regional and format settings automatically. But without vbscript how can we determine a date/time pattern for a user of a specific locale. Do we have to store a mapping between a locale and pattern somewhere and do the conversion at the server side ? Although date/time conversion is needed in most case, there's situation where only date matter for example if my birthday is 2 Feb 1980, it should be the same for all locale and no conversion should be done. How can we address this issue.

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• what is the point of heterogenous arrays?

  - by aharon

  I know that more-dynamic-than-Java languages, like Python and Ruby, often allow you to place objects of mixed types in arrays, like so: ["hello", 120, ["world"]] What I don't understand is why you would ever use a feature like this. If I want to store heterogenous data in Java, I'll usually create an object for it. For example, say a User has int ID and String name. While I see that in Python/Ruby/PHP you could do something like this: [["John Smith", 000], ["Smith John", 001], ...] this seems a bit less safe/OO than creating a class User with attributes ID and name and then having your array: [<User: name="John Smith", id=000>, <User: name="Smith John", id=001>, ...] where those <User ...> things represent User objects. Is there reason to use the former over the latter in languages that support it? Or is there some bigger reason to use heterogenous arrays? N.B. I am not talking about arrays that include different objects that all implement the same interface or inherit from the same parent, e.g.: class Square extends Shape class Triangle extends Shape [new Square(), new Triangle()] because that is, to the programmer at least, still a homogenous array as you'll be doing the same thing with each shape (e.g., calling the draw() method), only the methods commonly defined between the two.

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• Redeclared javascript global variable overrides old value in IE

  - by Yousuf Haider

  (creating a separate question after comments on this: http://stackoverflow.com/questions/2634410/javascript-redeclared-global-variable-overrides-old-value) I am creating a globally scoped variable using the square bracket notation and assigning it a value inside an external js file. In another js file I declare a var with the same name as the one I just created above. Note I am not assigning a value. Since this is a redeclaration of the same variable the old value should not be overriden as described here: http://www.w3schools.com/js/js_variables.asp Create 2 javascript files with the following content : Script1 //create global variable with square bracket notation window['y'] = 'old'; Script2 //redeclaration of the same variable var y; if (!y) y = 'new'; alert(y); //shows New instead of Old in IE Include these 2 files in your html file <html> <head></head> <body> <script type="text/javascript" src="my.js"></script> <script type="text/javascript" src="my2.js"></script> </body> </html> Opening this page in Firefox and Chrome alerts 'old' which is the expected behavior. However in IE 8 the page will actually alert 'new' Any ideas on why this happens on IE ?

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• C#: Wrong answer when finding "cool" numbers.

  - by user300484

  Hello you all! In my application, a "cool" number is a number that is both a square and a cube, like for example: 64 = 8^2 and 64 = 4^3. My application is supposed to find the number of "cool numbers" between a range given by the user. I wrote my code and the application runs fine, but it is giving me the wrong answer. Can you help me here please? for example: IMPUT 1 100 OUTPUT 1 using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { double a = Convert.ToDouble(Console.ReadLine()); // first number in the range double b = Convert.ToDouble(Console.ReadLine()); // second number in the range long x = 0; for (double i = a; i <= b; i++) { double cube = 1.0 / 3.0; double cuad = 1.0 / 2.0; double crt = Math.Pow(i, cube); // cube root double sqrt = Math.Pow(i, cuad); // square root if ((crt * 10) % 10 == 0 || (sqrt * 10) % 10 == 0) // condition to determine if it is a cool number. x++; } Console.WriteLine(x); Console.ReadLine(); } } }

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• OpenGL Colour Interpolation

  - by Will-of-fortune

  I'm currently working on an little project in C++ and OpenGL and am trying to implement a colour selection tool similar to that in photoshop, as below. However I am having trouble with interpolation of the large square. Working on my desktop computer with a 8800 GTS the result was similar but the blending wasn't as smooth. This is the code I am using: GLfloat swatch[] = { 0,0,0, 1,1,1, mR,mG,mB, 0,0,0 }; GLint swatchVert[] = { 400,700, 400,500, 600,500, 600,700 }; glVertexPointer(2, GL_INT, 0, swatchVert); glColorPointer(3, GL_FLOAT, 0, swatch); glDrawArrays(GL_QUADS, 0, 4); Moving onto my laptop with Intel Graphics HD 3000, this result was even worse with no change in code. I thought it was OpenGL splitting the quad into two triangles, so I tried rendering using triangles and interpolating the colour in the middle of the square myself but it still doesnt quite match the result I was hoping for. Any help would be appreciated. Thanks.

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• Button outside view... how to make it work

  - by Mike

  I have a UIImageView based class that creates objects with the following characteristics: a small image square and a UITextView below. If the user drags the object by the image it can drag it around. If the user taps on the UITextView the keyboard has to appear and the user can change the text on it. The objects created by the class are like this: 1) the object creates a 60x60 pixels frame 2) puts an image inside that frame 3) creates a UITextView and puts it below that 60x60 frame. So, as the class is a UIImageView based and it creates an image with 60x60 pixels and the UITextView is located outside that area, in theory the text view is outside the area the tapping are for that object. Obviously I could make the class create a big square to encompass the image and the text view, but that frame would be too big and I have the objects created by this class to be as close as possible when I add them to another view. I could also create the text views from the same view I created the objects, but I would have to manage each object and each correspondent text view and I need them to move together... so, I have a problem. Any ideas on a simplest way to do that?

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• Why does adding Crossover to my Genetic Algorithm give me worse results?

  - by MahlerFive

  I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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• Generic callbacks

  - by bobobobo

  Extends So, I'm trying to learn template metaprogramming better and I figure this is a good exercise for it. I'm trying to write code that can callback a function with any number of arguments I like passed to it. // First function to call int add( int x, int y ) ; // Second function to call double square( double x ) ; // Third func to call void go() ; The callback creation code should look like: // Write a callback object that // will be executed after 42ms for "add" Callback<int, int, int> c1 ; c1.func = add ; c1.args.push_back( 2 ); // these are the 2 args c1.args.push_back( 5 ); // to pass to the "add" function // when it is called Callback<double, double> c2 ; c2.func = square ; c2.args.push_back( 52.2 ) ; What I'm thinking is, using template metaprogramming I want to be able to declare callbacks like, write a struct like this (please keep in mind this is VERY PSEUDOcode) <TEMPLATING ACTION <<ANY NUMBER OF TYPES GO HERE>> > struct Callback { double execTime ; // when to execute TYPE1 (*func)( TYPE2 a, TYPE3 b ) ; void* argList ; // a stored list of arguments // to plug in when it is time to call __func__ } ; So for when called with Callback<int, int, int> c1 ; You would automatically get constructed for you by < HARDCORE TEMPLATING ACTION > a struct like struct Callback { double execTime ; // when to execute int (*func)( int a, int b ) ; void* argList ; // this would still be void*, // but I somehow need to remember // the types of the args.. } ; Any pointers in the right direction to get started on writing this?

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• Filter large amounts of data in a table w/ jQuery

  - by Bry4n

  I work for a transit agency and I have large amounts of data (mostly times), and I need a way to filter the data using two textboxes (To and From). I found jQuery quick search, but it seems to only work with one textbox. If anyone has any ideas via jQuery or some other client side library, that would be fantastic. Ideal example: To: [Textbox] From:[Textbox] <table> <tr> <td>69th street</td><td>5:00pm</td><td>5:06pm</td><td>5:10pm</td><td>5:20pm</td> </tr> <tr> <td>Millbourne</td><td>5:09pm</td><td>5:15pm</td><td>5:20pm</td><td>5:25pm</td> </tr> <tr> <td>Spring Garden</td><td>6:00pm</td><td>6:15pm</td><td>6:20pm</td><td>6:25pm</td> </tr> </table> So If I start typing in one of the stations in the To: textbox it either displays dynamically like the quick search or i have to press a button (either or) and then in the from: textbox. Lastly it shows me to: station and all its times on the left and the from: station and all its times on the right.

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• One big executable or many small DLL's?

  - by Patrick

  Over the years my application has grown from 1MB to 25MB and I expect it to grow further to 40, 50 MB. I don't use DLL's, but put everything in this one big executable. Having one big executable has certain advantages: Installing my application at the customer is really: copy and run. Upgrades can be easily zipped and sent to the customer There is no risk of having conflicting DLL's (where the customer has version X of the EXE, but version Y of the DLL) The big disadvantage of the big EXE is that linking times seem to grow exponentially. Additional problem is that a part of the code (let's say about 40%) is shared with another application. Again, the advantages are that: There is no risk on having a mix of incorrect DLL versions Every developer can make changes on the common code which speeds up developments. But again, this has a serious impact on compilation times (everyone compiles the common code again on his PC) and on linking times. The question http://stackoverflow.com/questions/2387908/grouping-dlls-for-use-in-executable mentions the possibility of mixing DLL's in one executable, but it looks like this still requires you to link all functions manually in your application (using LoadLibrary, GetProcAddress, ...). What is your opinion on executable sizes, the use of DLL's and the best 'balance' between easy deployment and easy/fast development?

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• Why are my events being called more than once?

  - by Arms

  In my Flash project I have a movieclip that has 2 keyframes. Both frames contain 1 movieclip each. frame 1 - Landing frame 2 - Game The flow of the application is simple: User arrives on landing page (frame 1) User clicks "start game" button User is brought to the game page (frame 2) When the game is over, the user can press a "play again" button which brings them back to step 1 Both Landing and Game movieclips are linked to separate classes that define event listeners. The problem is that when I end up back at step 1 after playing the game, the Game event listeners fire twice for their respective event. And if I go through the process a third time, the event listeners fire three times for every event. This keeps happening, so if I loop through the application flow 7 times, the event listeners fire seven times. I don't understand why this is happening because on frame 1, the Game movieclip (and I would assume its related class instance) does not exist - but I'm clearly missing something here. I've run into this problem in other projects too, and tried fixing it by first checking if the event listeners existed and only defining them if they didn't, but I ended up with unexpected results that didn't really solve the problem. I need to ensure that the event listeners only fire once. Any advice & insight would be greatly appreciated, thanks!

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• What can cause my code to run slower when the server JIT is activated?

  - by durandai

  I am doing some optimizations on an MPEG decoder. To ensure my optimizations aren't breaking anything I have a test suite that benchmarks the entire codebase (both optimized and original) as well as verifying that they both produce identical results (basically just feeding a couple of different streams through the decoder and crc32 the outputs). When using the "-server" option with the Sun 1.6.0_18, the test suite runs about 12% slower on the optimized version after warmup (in comparison to the default "-client" setting), while the original codebase gains a good boost running about twice as fast as in client mode. While at first this seemed to be simply a warmup issue to me, I added a loop to repeat the entire test suite multiple times. Then execution times become constant for each pass starting at the 3rd iteration of the test, still the optimized version stays 12% slower than in the client mode. I am also pretty sure its not a garbage collection issue, since the code involves absolutely no object allocations after startup. The code consists mainly of some bit manipulation operations (stream decoding) and lots of basic floating math (generating PCM audio). The only JDK classes involved are ByteArrayInputStream (feeds the stream to the test and excluding disk IO from the tests) and CRC32 (to verify the result). I also observed the same behaviour with Sun JDK 1.7.0_b98 (only that ist 15% instead of 12% there). Oh, and the tests were all done on the same machine (single core) with no other applications running (WinXP). While there is some inevitable variation on the measured execution times (using System.nanoTime btw), the variation between different test runs with the same settings never exceeded 2%, usually less than 1% (after warmup), so I conclude the effect is real and not purely induced by the measuring mechanism/machine. Are there any known coding patterns that perform worse on the server JIT? Failing that, what options are available to "peek" under the hood and observe what the JIT is doing there?

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• CCAnimate/CCAnimation cause inconsistent setTexture behavior in cocos2d on iPhone

  - by chillid

  Hi, I have a character that goes through multiple states. The state changes are reflected by means of a sprite image (texture) change. The state change is triggered by a user tapping on the sprite. This works consistently and quite well. I then added an animation during State0. Now, when the user taps - setTexture gets executed to change the texture to reflect State1, however some of the times (unpredictable) it does not change the texture. The code flows as below: // 1. // Create the animation sequence CGRect frame1Rect = CGRectMake(0,32,32,32); CGRect frame2Rect = CGRectMake(32,32,32,32); CCTexture2D* texWithAnimation = [[CCTextureCache sharedTextureCache] addImage:@"Frames0_1_thinkNthickoutline32x32.png"]; id anim = [[[CCAnimation alloc] initWithName:@"Sports" delay:1/25.0] autorelease]; [anim addFrame:[CCSpriteFrame frameWithTexture:texWithAnimation rect:frame1Rect offset:ccp(0,0)]]; [anim addFrame:[CCSpriteFrame frameWithTexture:texWithAnimation rect:frame2Rect offset:ccp(0,0)]]; // Make the animation sequence repeat forever id myAction = [CCAnimate actionWithAnimation: anim restoreOriginalFrame:NO]; // 2. // Run the animation: sports = [[CCRepeatForever alloc] init]; [sports initWithAction:myAction]; [self.sprite runAction:sports]; // 3. stop action on state change and change texture: NSLog(@"Stopping action"); [sprite stopAction:sports]; NSLog(@"Changing texture for kCJSports"); [self setTexture: [[CCTextureCache sharedTextureCache] addImage:@"SportsOpen.png"]]; [self setTextureRect:CGRectMake(0,0,32,64)]; NSLog(@"Changed texture for kCJSports"); Note that all the NSLog lines get logged - and the texture RECT changes - but the image/texture changes only some of the times - fails for around 10-30% of times. Locking/threading/timing issue somewhere? My app (game) is single threaded and I only use the addImage and not the Async version. Any help much appreciated.

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• Projective transformation

  - by mcwehner

  Given two image buffers (assume it's an array of ints of size width * height, with each element a color value), how can I map an area defined by a quadrilateral from one image buffer into the other (always square) image buffer? I'm led to understand this is called "projective transformation". I'm also looking for a general (not language- or library-specific) way of doing this, such that it could be reasonably applied in any language without relying on "magic function X that does all the work for me". An example: I've written a short program in Java using the Processing library (processing.org) that captures video from a camera. During an initial "calibrating" step, the captured video is output directly into a window. The user then clicks on four points to define an area of the video that will be transformed, then mapped into the square window during subsequent operation of the program. If the user were to click on the four points defining the corners of a door visible at an angle in the camera's output, then this transformation would cause the subsequent video to map the transformed image of the door to the entire area of the window, albeit somewhat distorted.

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• World's Most Challening MySQL SQL Query (least I think so...)

  - by keruilin

  Whoever answers this question can claim credit for solving the world's most challenging SQL query, according to yours truly. Working with 3 tables: users, badges, awards. Relationships: user has many awards; award belongs to user; badge has many awards; award belongs to badge. So badge_id and user_id are foreign keys in the awards table. The business logic at work here is that every time a user wins a badge, he/she receives it as an award. A user can be awarded the same badge multiple times. Each badge is assigned a designated point value (point_value is a field in the badges table). For example, BadgeA can be worth 500 Points, BadgeB 1000 Points, and so on. As further example, let's say UserX won BadgeA 10 times and BadgeB 5 times. BadgeA being worth 500 Points, and BadgeB being worth 1000 Points, UserX has accumulated a total of 10,000 Points ((10 x 500) + (5 x 1000)). The end game here is to return a list of top 50 users who have accumulated the most badge points. Can you do it?

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• Translation of a RoR view to Java

  - by mnml

  Hi, for some reasons I am trying to translate the following RoR view code to a GSP view: List<Object> objectscontains the data I want to display in 3 columns <% modulo_objects = @objects.length % 3 base = @objects.length / 3 base = base.ceil case modulo_objects when 0 cols = [base, base, base] when 1 cols = [base, base + 1, base] when 2 cols = [base + 1, base, base + 1] end counter = 0 %> <% 3.times do |i| %> <td width="220" align="center" style="padding-right: 15px;"> <% cols[i].times do %> <h1><a href="/objects/show/<%= @objects[counter].urlname %>" ><%= @objects[counter].name %></a></h1> <% counter = counter + 1 %> <% end %> </td> <% end %> This is what I got so far: #{extends 'main.html' /} %{ modulo_objects = objects.size() % 3 base = objects.size() / 3 base = Math.ceil(base) if(modulo_objects == 0) cols = [base, base, base] else if(modulo_objects == 1) cols = [base, base + 1, base] else if(modulo_objects == 2) cols = [base + 1, base, base + 1] endif counter = 0 }% #{list items:1..3, as:'i'} <td width="220" align="center" style="padding-right: 15px;"> #{list items:cols[i]} <a href="@{Objects.show(objects.get(counter).name.replaceAll(" ", "-"))}" >${objects.get(counter).name}</a> %{ counter = counter + 1 }% #{/list} </td> #{/list} The idea is to keep the items organised in 3 columns like 1|0|1 4|5|4 or 5|4|5 for example, I don't really understand if #{list items:cols[i]} will reproduce ruby's cols[i].times do. So far the Java view is does not display more than two elements.

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• Using same onmouseover function for multiple objects

  - by phpscriptcoder

  I'm creating a building game in JavaScript and PHP that involves a grid. Each square in the grid is a div, with an own onmouseover and onmousedown function: for(x=0; x < width; x++) { for(y=0; y < height; y++) { var div = document.createElement("div"); //... div.onmouseclick = function() {blockClick(x, y)} div.onmouseover = function() {blockMouseover(x, y)} game.appendChild(div); } } But, all of the squares seem to have the x and y of the last square that was added. I can sort of see why this is happening - it is making a pointer to x and y instead of cloning the variables - but how could I fix it? I even tried for(x=0; x < width; x++) { for(y=0; y < height; y++) { var div = document.createElement("div"); var myX = x; var myY = y; div.onmouseclick = function() {blockClick(myX, myY)} div.onmouseover = function() {blockMouseover(myX, myY)} game.appendChild(div); } } with the same result. I was using div.setAttribute("onmouseover", ...) which worked in Firefox, but not IE. Thanks!

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• optimize 2D array in C++

  - by Hristo

  I'm dealing with a 2D array with the following characteristics: const int cols = 500; const int rows = 100; int arr[rows][cols]; I access array arr in the following manner to do some work: for(int k = 0; k < T; ++k) { // for each trainee myscore[k] = 0; for(int i = 0; i < N; ++i) { // for each sample for(int j = 0; j < E[i]; ++j) { // for each expert myscore[k] += delta(i, anotherArray[k][i], arr[j][i]); } } } So I am worried about the array 'arr' and not the other one. I need to make this more cache-friendly and also boost the speed. I was thinking perhaps transposing the array but I wasn't sure how to do that. My implementation turns out to only work for square matrices. How would I make it work for non-square matrices? Also, would mapping the 2D array into a 1D array boost the performance? If so, how would I do that? Finally, any other advice on how else I can optimize this... I've run out of ideas, but I know that arr[j][i] is the place where I need to make changes because I'm accessing columns by columns instead of rows by rows so that is not cache friendly at all. Thanks, Hristo

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• Why are my event listeners firing more than once?

  - by Arms

  In my Flash project I have a movieclip that has 2 keyframes. Both frames contain 1 movieclip each. frame 1 - Landing frame 2 - Game The flow of the application is simple: User arrives on landing page (frame 1) User clicks "start game" button User is brought to the game page (frame 2) When the game is over, the user can press a "play again" button which brings them back to step 1 Both Landing and Game movieclips are linked to separate classes that define event listeners. The problem is that when I end up back at step 1 after playing the game, the Game event listeners fire twice for their respective event. And if I go through the process a third time, the event listeners fire three times for every event. This keeps happening, so if I loop through the application flow 7 times, the event listeners fire seven times. I don't understand why this is happening because on frame 1, the Game movieclip (and I would assume its related class instance) does not exist - but I'm clearly missing something here. I've run into this problem in other projects too, and tried fixing it by first checking if the event listeners existed and only defining them if they didn't, but I ended up with unexpected results that didn't really solve the problem. I need to ensure that the event listeners only fire once. Any advice & insight would be greatly appreciated, thanks!

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