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• Java Thread - Synchronization issue

  - by Yatendra Goel

  From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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• Multi-threading concept and lock in c#

  - by Neeraj

  I read about lock, though not understood nothing at all. My question is why do we use a un-used object and lock that and how this makes something thread-safe or how this helps in multi-threading ? Isn't there other way to make thread-safe code. public class test { private object Lock { get; set; } ... lock (this.Lock) { ... } ... } Sorry is my question is very stupid, but i don't understand, although i've used it many times.

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• Help me find article on Multi-threading and Event Handling in Java

  - by JDR

  I once read an article on how to properly write event handlers for multi-threading in Java, but I can't for the life of me find it anymore. It described the pitfalls and potentials for deadlocks that can occur when firing events (not Swing events mind you, but general events like model update notifications). To clarify, the situation would be as such: // let's say this is code from an MVC model somewhere public void setSomeProperty(String myProperty){ if(!this.myProperty.equals(myProperty)){ this.myProperty = myProperty; fireMyPropertyChangedEvent(...); } } The article described how passing control to arbitrary external listener code was a potential cause for deadlock. I now find myself in a situation where I need to fire such events in a multithreaded environment and I would very much like to read the article again to see what it has to say before I continue. Does anyone know the article I'm referring to? I believe it came as a (fairly short) PDF. It started off with an initial naive implementation and incrementally pointed out flaws and improved upon it. It ended with a sort of final proper-way-to-fire-multithreaded-events. I've searched endlessly in my browse history and on google, but all I could find were endless amounts topics on Swing event dispatch threads. Thank you.

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• Download multiple files in background in Android

  - by Addev

  Basically I'm trying to make a little app for watching offline content. So there's a moment where the user selects to download the contents (and the app should download about 300 small files and images). I'd like to show the user how does the process go if he enters the proper activity. Showing a list of all the files, telling what has been already downloaded, in progress or waiting for download. My problem is that I really don't know what approach to take for achieve this. Since the download should last until finished I imagine the solution is an Service, but whats best? an IntentService, a Bound Service or an Standard Service calling a startService() for each download? And how can I keep my objects updated for displaying them later? should I use a database or objects in memory? Thanks

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• Thread-safe blocking queue implementation on .NET

  - by Shrike

  Hello. I'm looking for an implementation of thread-safe blocking queue for .NET. By "thread-safe blocking queue" I mean: - thread-safe access to a queue where Dequeue method call blocks a thread untill other thread puts (Enqueue) some value. By the moment I'v found this one: http://www.eggheadcafe.com/articles/20060414.asp (But it's for .NET 1.1). Could someone comment/criticize correctness of this implementation. Or suggest some another one. Thanks in advance.

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• Understanding java's native threads and the jvm

  - by Moev4

  I understand that the jvm is itself an application that turns the bytecode of the java executable into native machine code, but when using native threads I have some questions that I just cannot seem to answer. Does every thread create their own instance of the jvm to handle their particular execution? If not then does the jvm have to have some way to schedule which thread it will handle next, if so wouldn't this render the multi-threaded nature of java useless since only one thread can be ran at a time?

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• Why wait should always be in synchronized block

  - by diy

  Hi gents, We all know that in order to invoke Object.wait() , this call must be placed in synchronized block,otherwise,IllegalMonitorStateException is thrown.But what's the reason for making this restriction?I know that wait() releases the monitor, but why do we need to explicitly acquire the monitor by making particular block synchronized and then release the monitor by calling wait() ? What is the potential damage if it was possible to invoke wait() outside synch block, retaining it's semantics - suspending the caller thread ? Thanks in advance

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• How solve consumer/producer task using semaphores

  - by user1074896

  I have SimpleProducerConsumer class that illustrate consumer/producer problem (I am not sure that it's correct). public class SimpleProducerConsumer { private Stack<Object> stack = new Stack<Object>(); private static final int STACK_MAX_SIZE = 10; public static void main(String[] args) { SimpleProducerConsumer pc = new SimpleProducerConsumer(); new Thread(pc.new Producer(), "p1").start(); new Thread(pc.new Producer(), "p2").start(); new Thread(pc.new Consumer(), "c1").start(); new Thread(pc.new Consumer(), "c2").start(); new Thread(pc.new Consumer(), "c3").start(); } public synchronized void push(Object d) { while (stack.size() >= STACK_MAX_SIZE) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } stack.push(new Object()); System.out.println("push " + Thread.currentThread().getName() + " " + stack.size()); notify(); } public synchronized Object pop() { while (stack.size() == 0) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(50); } catch (InterruptedException e) { e.printStackTrace(); } stack.pop(); System.out.println("pop " + Thread.currentThread().getName() + " " + stack.size()); notify(); return null; } class Consumer implements Runnable { @Override public void run() { while (true) { pop(); } } } class Producer implements Runnable { @Override public void run() { while (true) { push(new Object()); } } } } I found simple realization of semaphore(here:http://docs.oracle.com/javase/tutorial/essential/concurrency/guardmeth.html I know that there is concurrency package) How I need to change code to exchange java objects monitors to my custom semaphore. (To illustrate C/P problem using semaphores) Semaphore: class Semaphore { private int counter; public Semaphore() { this(0); } public Semaphore(int i) { if (i < 0) throw new IllegalArgumentException(i + " < 0"); counter = i; } public synchronized void release() { if (counter == 0) { notify(); } counter++; } public synchronized void acquire() throws InterruptedException { while (counter == 0) { wait(); } counter--; } }

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• Limiting object allocation over multiple threads

  - by John

  I have an application which retrieves and caches the results of a clients query. The client then requests different chunks of data and the application sends the relevant results and removes them from the cache. A new requirement for this application is that there needs to be a run-time configurable maximum number of results which may be cached. I've taken the naive approach and implemented this by using a counter under a lock which is incremented every time a result is cached and decremented whenever a result is removed from the cache. Unfortunately, this has drastically reduced the applications performance when processing a large number of concurrent requests. I have tried both a critical section lock and spin-lock; the performance improves a bit with a spin-lock, but is still unacceptably slow. Is there a better way to solve this problem which may improve performance? Right now I have a thread pool that services requests and each request is tied to a Request object which stores that cached results for that particular request. Here is a simplified pseudo code version of my current implementation: void ResultCallback( Result result, Request *request ) { lock totalResultsCached lock cachedLimit if( totalResultsCached + 1 > cachedLimit ) { unlock cachedLimit unlock totalResultsCached //cancel the request return; } ++totalResultsCached; unlock cachedLimit unlock totalResultsCached request.add(result) } void SendResults( int resultsToSend, Request *request ) { while ( resultsToSend > 0 ) { send(request.remove()) lock totalResultsCached --totalResultsCached unlock totalResultsCached --resultsToSend; } }

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• Thread class closing from other Class (Activity) with protected void onStop() Android

  - by user1761337

  I have a Problem with Closing the Thread. I will Closing the Thread with onStop,onPause and onDestroy. This is my Source in the Activity Class: @Override protected void onStop(){ super.onStop(); finish(); } @Override protected void onPause() { super.onPause(); finish(); } @Override public void onDestroy() { this.mWakeLock.release(); super.onDestroy(); } And the Thread Class: public class GameThread extends Thread { private SurfaceHolder mSurfaceHolder; private Handler mHandler; private Context mContext; private Paint mLinePaint; private Paint blackPaint; //for consistent rendering private long sleepTime; //amount of time to sleep for (in milliseconds) private long delay=1000/30; //state of game (Running or Paused). int state = 1; public final static int RUNNING = 1; public final static int PAUSED = 2; public final static int STOPED = 3; GameSurface gEngine; public GameThread(SurfaceHolder surfaceHolder, Context context, Handler handler,GameSurface gEngineS){ //data about the screen mSurfaceHolder = surfaceHolder; mHandler = handler; mContext = context; gEngine=gEngineS; } //This is the most important part of the code. It is invoked when the call to start() is //made from the SurfaceView class. It loops continuously until the game is finished or //the application is suspended. private long beforeTime; @Override public void run() { //UPDATE while (state==RUNNING) { Log.d("State","Thread is runnig"); //time before update beforeTime = System.nanoTime(); //This is where we update the game engine gEngine.Update(); //DRAW Canvas c = null; try { //lock canvas so nothing else can use it c = mSurfaceHolder.lockCanvas(null); synchronized (mSurfaceHolder) { //clear the screen with the black painter. //reset the canvas c.drawColor(Color.BLACK); //This is where we draw the game engine. gEngine.doDraw(c); } } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } this.sleepTime = delay-((System.nanoTime()-beforeTime)/1000000L); try { //actual sleep code if(sleepTime>0){ this.sleep(sleepTime); } } catch (InterruptedException ex) { Logger.getLogger(GameThread.class.getName()).log(Level.SEVERE, null, ex); } while (state==PAUSED){ Log.d("State","Thread is pausing"); try { this.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }} How i can close the Thread from Activity Class??

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• C++0x thread interruption

  - by Nicola Bonelli

  According to the C++0x final draft, there's no way to request a thread to terminate. That said, if required we need to implement a do-it-yourself solution. In your opinion, what's the best solution? Designing your own cooperative 'interruption mechanism' or going native?

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• Windows service thread not updating database until complete

  - by dfarney

  I have a windows service with a FileSystemWatcher. When a new file is dropped in my folder a new thread is created, started, and I begin processing the file. Throughout this process I am making updates to the database (Linq to SQL) to keep track of the file's processing progress. Problem is none of my database updates are reflected throughout the process, just an update after everything has been completed. Any ideas? Note: when doing dev/testing my code was in an aspx page and worked great, but when I put it in a windows service I no longer get the progress updates. Thanks!

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• When Should I Use Threads?

  - by cam

  As far as I'm concerned, the ideal amount of threads is 3: one for the UI, one for CPU resources, and one for IO resources. But I'm probably wrong. I'm just getting introduced to them, but I've always used one for the UI and one for everything else. When should I use threads and how? How do I know if I should be using them?

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• logging one thread in Java using log4j

  - by Javier

  I have an web application written in Java, and I have a thread-pool. The application is huge, and I cannot make major changes, for example, I cannot change log4j. I am executing a batch process in the thread pool, and I want to log everything that goes is executed to execute that process. There will always be just one thread active in the thread pool. Any ideas of how can I do that?

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• Reducing lag when downloading large amount of data from webpage

  - by Mahir

  I am getting data via RSS feeds and displaying each article in a table view cell. Each cell has an image view, set to a default image. If the page has an image, the image is to be replaced with the image from the article. As of now, each cell downloads the source code from the web page, causing the app to lag when I push the view controller and when I try scrolling. Here is what I have in the cellForRowAtIndexPath: method. NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; cell.picture.image = image; Someone suggested using NSOperationQueue. Would this way be a good solution? EDIT: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *MyIdentifier = @"FeedCell"; LMU_LAL_FeedCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier]; if (cell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"LMU_LAL_FeedCell" owner:self options:nil]; cell = (LMU_LAL_FeedCell*) [nib objectAtIndex:0]; } int storyIndex = [indexPath indexAtPosition: [indexPath length] - 1]; NSString *untrimmedTitle = [[stories objectAtIndex: storyIndex] objectForKey: @"title"]; cell.title.text = [untrimmedTitle stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; CGSize maximumLabelSize = CGSizeMake(205,9999); CGSize expectedLabelSize = [cell.title.text sizeWithFont:cell.title.font constrainedToSize:maximumLabelSize]; //adjust the label to the the new height. CGRect newFrame = cell.title.frame; newFrame.size.height = expectedLabelSize.height; cell.title.frame = newFrame; //position frame of date label CGRect dateNewFrame = cell.date.frame; dateNewFrame.origin.y = cell.title.frame.origin.y + cell.title.frame.size.height + 1; cell.date.frame = dateNewFrame; cell.date.text = [self formatDateAtIndex:storyIndex]; dispatch_queue_t someQueue = dispatch_queue_create("cell background queue", NULL); dispatch_async(someQueue, ^(void){ NSError *error = nil; NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; dispatch_async(dispatch_get_main_queue(), ^(void){ cell.picture.image = image; }); }) //error: expected expression } return cell; //error: expected identifier } //error extraneous closing brace

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• C# WinForms populating TreeView from List<myObj>

  - by user743354

  I have this structure of classes: public class L3Message { public int Number { get; set; } public string MessageName { get; set; } public string Device { get; set; } public string Time { get; set; } public string ScramblingCode { get; set; } public List<Parameter> Parameters { get; set; } public L3Message() { Parameters = new List<Parameter>(); } } public class Parameter { public int numOfWhitespaces { get; set; } public string ParameterName { get; set; } public string ParameterValue { get; set; } public Parameter Parent { get; set; } public List<Parameter> SubParameters { get; set; } public Parameter() { SubParameters = new List<Parameter>(); } } So, as return type from one of my Methods I have List of L3Messages (List < L3Message ), and I need to map that to TreeView in WinForms (populate TreeView from that List). If possible, I would like to that in separate thread. How can I achieve that?

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• Processes Allocation in .Net

  - by mayap

  I'm writing some program which should perform calculations concurrently according to inputs which reach the system all the time. I'm considering 2 approaches to allocate "calculation" processes: Allocating processes in the system initialization, insert the ids to Processes table, and each time I want to perform calculation, I will check in the table which process is free. The questions: can I be sure that those processes are only for my use and that the operating system doesn't use them? Not allocating processes in advance. Each time when calculation should be done ask the operating system for free process. I need to know the following inputs from a "calculation" process: When calculation is finished and also if it succeeded or failed If a processes has failed I need to assign the calculation to another process Thanks in advance. Any help would be appreciated.

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• MonoTouch Load image in background

  - by user1058951

  I am having a problem trying to load an image and display it using System.Threading.Task My Code is as follows Task DownloadTask { get; set; } public string Instrument { get; set; } public PriceChartViewController(string Instrument) { this.Instrument = Instrument; DownloadTask = Task.Factory.StartNew(() => { }); } private void LoadChart(ChartType chartType) { NSData data = new NSData(); DownloadTask = DownloadTask.ContinueWith(prevTask => { try { UIApplication.SharedApplication.NetworkActivityIndicatorVisible = true; NSUrl nsUrl = new NSUrl(chartType.Uri(Instrument)); data = NSData.FromUrl(nsUrl); } finally { UIApplication.SharedApplication.NetworkActivityIndicatorVisible = false; } }); DownloadTask = DownloadTask.ContinueWith(t => { UIImage image = new UIImage(data); chartImageView = new UIImageView(image); chartImageView.ContentScaleFactor = 2f; View.AddSubview(chartImageView); this.Title = chartType.Title; }, CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, TaskScheduler.FromCurrentSynchronizationContext()); } The second Continue with does not seem to be being called? Initially my code looked like the following without the background processing and it worked perfectly. private void oldLoadChart(ChartType chartType) { UIApplication.SharedApplication.NetworkActivityIndicatorVisible = true; NSUrl nsUrl = new NSUrl(chartType.Uri(Instrument)); NSData data = NSData.FromUrl(nsUrl); UIImage image = new UIImage(data); chartImageView = new UIImageView(image); chartImageView.ContentScaleFactor = 2f; View.AddSubview(chartImageView); this.Title = chartType.Title; UIApplication.SharedApplication.NetworkActivityIndicatorVisible = false; } Does anyone know what I am doing wrong?

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• How do I wait for all other threads to finish their tasks?

  - by Mike

  I have several threads consuming tasks from a queue using something similar to the code below. The problem is that there is one type of task which cannot run while any other tasks are being processed. Here is what I have: while (true) // Threaded code { while (true) { lock(locker) { if (close_thread) return; task = GetNextTask(); // Get the next task from the queue } if (task != null) break; wh.WaitOne(); // Wait until a task is added to the queue } task.Run(); } And this is kind of what I need: while (true) { while (true) { lock(locker) { if (close_thread) return; if (disable_new_tasks) { task = null; } else { task = GetNextTask(); } } if (task != null) break; wh.WaitOne(); } if(!task.IsThreadSafe()) { // I would set this to false inside task.Run() at // the end of the non-thread safe task disable_new_tasks = true; Wait_for_all_threads_to_finish_their_current_tasks(); } task.Run(); } The problem is I don't know how to achive this without creating a mess.

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• Threading Problems in ActionScript 2.0?

  - by yar

  Is it possible to have concurrency problems (thread competition) in an onEnterFrame method in ActionScript 2.0? I have written this cheesy code as a guard: if (!busy) { // I suspect some threading problems: is that even possible in flash busy = true; movePanels(); busy = false; } but this is no assurance against thread competition. If so, how can I do a basic semaphore/lock? Note: I suspect threading problems in my app, but if they're impossible, I'll check my code differently.

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• A generic C++ library that provides QtConcurrent functionality?

  - by Lucas

  QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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• Heroku DJango app development on Windows

  - by Cliff

  I'm trying to start a Django app on Heroku using Windows and I'm getting stuck on the following error when I try to pip install psycopg2: Downloading/unpacking psycopg2 Downloading psycopg2-2.4.5.tar.gz (719Kb): 719Kb downloaded Running setup.py egg_info for package psycopg2 Error: pg_config executable not found. Please add the directory containing pg_config to the PATH or specify the full executable path with the option: python setup.py build_ext --pg-config /path/to/pg_config build ... or with the pg_config option in 'setup.cfg'. Complete output from command python setup.py egg_info: running egg_info creating pip-egg-info\psycopg2.egg-info writing pip-egg-info\psycopg2.egg-info\PKG-INFO writing top-level names to pip-egg-info\psycopg2.egg-info\top_level.txt writing dependency_links to pip-egg-info\psycopg2.egg-info\dependency_links.txt writing manifest file 'pip-egg-info\psycopg2.egg-info\SOURCES.txt' warning: manifest_maker: standard file '-c' not found I've googled the error and it seems you need libpq-dev python-dev as dependencies for postgres under Python. I also turned up a link that says you gt into trouble if you don't have the postgres bin folder in your Path so I installed Postgres manually and tried again. This time I get: error: Unable to find vcvarsall.bat I am still a python N00b so I am lost. Could someone point me in a general direction?

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• Is there any cross-platform threading library in C/C++?

  - by NumberFour

  Hello, I'm looking for some easy to use cross-platform threading library written in C/C++. What's your opinion on boost::thread or Pthreads? Does Pthreads run only on POSIX compliant systems? What about the threading support in the Qt library? Thanks for any hints.

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• Implementing deadlock condition

  - by Bhaskar

  I am trying to implementing deadlock condition but somehow I am not able to get it working. Both the threads Thread1 and Thread2 are entering in the run function but only one of them enters in Sub/Sum depending on who entered run first. Example : if Thread2 entered run first the it will call sub() and Thread1 never calls sum(). I have also added sleep time so that Thread2 sleeps before calling sum() and Thread1 gets enough time to enter Sum() but Thread1 never enters. public class ExploringThreads { public static void main(String[] args) { // TODO Auto-generated method stub threadexample a1 = new threadexample(); Thread t1 = new Thread(a1, "Thread1"); Thread t2 = new Thread(a1,"Thread2"); t1.start(); t2.start(); } } class threadexample implements Runnable{ public int a = 10; public void run(){ if(Thread.currentThread().getName().equals("Thread1")) sum(); else if(Thread.currentThread().getName().equals("Thread2")) sub(); } public synchronized void sum() { try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+"In Sum"); sub(); } public synchronized void sub() { try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+"In Sub"); sum(); } }

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• Crossthread exception and invokerequired solution doesn't change my control value

  - by Pilouk

  EDIT Solution : Here i'm setting my byref value in each object then i'm running a backgroundworker Private Sub TelechargeFichier() Dim DocManquant As Boolean = False Dim docName As String = "" Dim lg As String = "" Dim telechargementFini As Boolean = False lblMessage.Text = EasyDealChangeLanguage.Instance.GetStringFromResourceName("1478") prgBar.Maximum = m_listeFichiers.Count For i As Integer = 0 To m_listeFichiers.Count - 1 m_listeFichiers(i).Set_ByRefLabel(lblMessage) m_listeFichiers(i).Set_ByRefPrgbar(prgBar) m_listeThreads.Add(New Thread(AddressOf m_listeFichiers(i).DownloadMe)) Next m_bgWorker = New BackgroundWorker m_bgWorker.WorkerReportsProgress = True AddHandler m_bgWorker.DoWork, AddressOf DownloadFiles m_bgWorker.RunWorkerAsync() ''Completed 'lblMessage.Text = EasyDealChangeLanguage.Instance.GetStringFromResourceName("1383") 'Me.DialogResult = System.Windows.Forms.DialogResult.OK End Sub Here is my downloadFiles function : Note that each start will do the downloadMe function see below too Private Sub DownloadFiles(sender As Object, e As DoWorkEventArgs) For i As Integer = 0 To m_listeThreads.Count - 1 m_listeThreads(i).Start() Next For i As Integer = 0 To m_listeThreads.Count - 1 m_listeThreads(i).Join() Next End Sub I have multiple thread that each will download a ftp file. I would like that each file that have been completed will set a value to a progress bar and a label from my UI thread. For some reason invokerequired never change to false. Here is my little function that start all the thread Private Sub TelechargeFichier() Dim DocManquant As Boolean = False Dim docName As String = "" Dim lg As String = "" Dim telechargementFini As Boolean = False lblMessage.Text = EasyDealChangeLanguage.Instance.GetStringFromResourceName("1478") prgBar.Maximum = m_listeFichiers.Count For i As Integer = 0 To m_listeFichiers.Count - 1 m_listeFichiers(i).Set_ByRefLabel(lblMessage) m_listeFichiers(i).Set_ByRefPrgbar(prgBar) m_listeThreads.Add(New Thread(AddressOf m_listeFichiers(i).DownloadMe)) Next For i As Integer = 0 To m_listeThreads.Count - 1 m_listeThreads(i).Start() Next For i As Integer = 0 To m_listeThreads.Count - 1 m_listeThreads(i).Join() Next 'Completed lblMessage.Text = EasyDealChangeLanguage.Instance.GetStringFromResourceName("1383") Me.DialogResult = System.Windows.Forms.DialogResult.OK End Sub Here my property that hold the Byref control from the UI thread. This is in my object which content the addressof function that will download the file (DownloadMe) Public Sub Set_ByRefPrgbar(ByRef prgbar As ProgressBar) m_prgBar = prgbar End Sub Public Sub Set_ByRefLabel(ByRef lbl As EasyDeal.Controls.EasyDealLabel3D) m_lblMessage = lbl End Sub Here is the download function : Public Sub DownloadMe() Dim ftpReq As FtpWebRequest Dim ftpResp As FtpWebResponse = Nothing Dim streamInput As Stream Dim fileStreamOutput As FileStream Try ftpReq = CType(WebRequest.Create(EasyDeal.Controls.Common.FTP_CONNECTION & m_downloadFtpPath & m_filename), FtpWebRequest) ftpReq.Credentials = New NetworkCredential(FTP_USER, FTP_PASS) ftpReq.Method = WebRequestMethods.Ftp.DownloadFile ftpResp = ftpReq.GetResponse streamInput = ftpResp.GetResponseStream() fileStreamOutput = New FileStream(m_outputPath, FileMode.Create, FileAccess.ReadWrite) ReadWriteStream(streamInput, fileStreamOutput) Catch ex As Exception 'Au pire la fichier sera pas downloader Finally If ftpResp IsNot Nothing Then ftpResp.Close() End If Dim nomFichier As String = m_displaynameEN If EasyDealChangeLanguage.GetCurrentLanguageTypes = EasyDealChangeLanguage.EnumLanguageType.Francais Then nomFichier = m_displaynameFR End If If m_lblMessage IsNot Nothing Then EasyDealCommon.TH_SetControlText(m_lblMessage, String.Format(EasyDealChangeLanguage.Instance.GetStringFromResourceName("1479"), nomFichier)) End If If m_prgBar IsNot Nothing Then EasyDealCommon.TH_SetPrgValue(m_prgBar, 1) End If End Try End Sub Here is the crossthread invoke solution function : Public Sub TH_SetControlText(ByVal ctl As Control, ByVal text As String) If ctl.InvokeRequired Then ctl.BeginInvoke(New Action(Of Control, String)(AddressOf TH_SetControlText), ctl, text) Else ctl.Text = text End If End Sub Public Sub TH_SetPrgValue(ByVal prg As ProgressBar, ByVal value As Integer) If prg.InvokeRequired Then prg.BeginInvoke(New Action(Of ProgressBar, Integer)(AddressOf TH_SetPrgValue), prg, value) Else prg.Value += value End If End Sub The problem is the invokerequired never get to false it actually goes in to beginInvoke but never end in the Else section to set the value.

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