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• iPhone equivalent of Application.DoEvents();

  - by BahaiResearch.com

  iPHone: We use MonoTouch, but Obj-C answers are ok. My singleton domain object takes a while to get all the data so it runs internally parts of the fetch in a thread. I need to inform the UI that the domain is done. Currently I do this. Is there a better way? In WinForms I would call Application.DoEvents() instead of Thread Sleep. PlanDomain domain = PlanDomain.Instance (); while (domain.IsLoadingData) { Thread.Sleep (100); //this is the main UI thread } TableView.Hidden = false; TableView.Source = new TableSource (this); TableView.ReloadData ();

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• WPF Dispatcher {"The calling thread cannot access this object because a different thread owns it."}

  - by user359446

  first I need to say that I´m noob with WPF and C#. Application: Create Mandelbrot Image (GUI) My disptacher works perfektly this this case: private void progressBarRefresh(){ while ((con.Progress) < 99) { progressBar1.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { progressBar1.Value = con.Progress; } )); } } I get the Message (Title) when tring to do this with the below code: bmp = BitmapSource.Create(width, height, 96, 96, pf, null, rawImage, stride); this.Dispatcher.Invoke(DispatcherPriority.Send, new Action(delegate { img.Source = bmp; ViewBox.Child = img; //vllt am schluss } )); I will try to explain how my program works. I created a new Thread (because GUI dont response) for the calculation of the pixels and the colors. In this Thread(Mehtod) I´m using the Dispatcher to Refresh my Image in the ViewBox after the calculations are ready. When I´m dont put the calculation in a seperate Thread then I can refresh or build my Image.

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• Ramifications of CheckForIllegalCrossThreadCalls=false

  - by Ron Skufca

  I recently updated an application from VS2003 to VS2008 and I knew I would be dealing with a host of "Cross-thread operation not valid: Control 'myControl' accessed from a thread other than the thread it was created on" I am handling this in what I beleive is the correct way (see code sample below). I am running into numerous controls that are going to need a similar fix. Not wanting to have similar code for every label, textbox etc.. that are being accessed by a non UI thread. What are the ramifications of just setting the CheckForIllegalCrossThreadCalls = false for the entire app? I found a CodeProject article with various workarounds and a warning at the bottom to NOT set the property. I am looking for other opinions/experiences on this issue. private void ShowStatus(string szStatus) { try { if (this.statusBar1.InvokeRequired) { BeginInvoke(new MethodInvoker(delegate() { ShowStatus(szStatus); })); } else { statusBar1.Panels[0].Text = szStatus; } } catch (Exception ex) { LogStatus.WriteErrorLog(ex, "Error", "frmMNI.ShowStatus()"); } }

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• Understanding Thread/BeginInvoke? [beginner]

  - by Moberg

  Consider the code: class Work { public void DoStuff(string s) { Console.WriteLine(s); // .. whatever } } class Master { private readonly Work work = new Work(); public void Execute() { string hello = "hello"; // (1) is this an ugly hack ? var thread1 = new Thread(new ParameterizedThreadStart(o => this.work.DoStuff((string)o))); thread1.Start(hello); thread1.Join(); // (2) is this similar to the one above? new Action<string>(s => this.work.DoStuff(s)).BeginInvoke(hello, null, null); } } Is (1) an acceptable way of easy starting some work in a seperate thread? If not a better alternative would be much appreciated. Is (2) doing the same? I guess what I ask is if a new thread is started, or.. Hope you can help a beginner to a better understanding :) /Moberg

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• Ruby Thread with "watchdog"

  - by Sergio Campamá

  I'm implementing a ruby server for handling sockets being created from GPRS modules. The thing is that when the module powers down, there's no indication that the socket closed. I'm doing threads to handle multiple sockets with the same server. What I'm asking is this: Is there a way to use a timer inside a thread, reset it after every socket input, and that if it hits the timeout, closes the thread? Where can I find more information about this? EDIT: Code example that doesn't detect the socket closing require 'socket' server = TCPServer.open(41000) loop do Thread.start(server.accept) do |client| puts "Client connected" begin loop do line = client.readline open('log.txt', 'a') { |f| f.puts line.strip } end rescue puts "Client disconnected" end end end

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• Events raised by BackgroundWorker not executed on expected thread

  - by Topdown

  A winforms dialog is using BackgroundWorker to perform some asynchronous operations with significant success. On occasion, the async process being run by the background worker will need to raise events to the winforms app for user response (a message that asks the user if they wish to cancel), the response of which captured in an CancelEventArgs type of the event. Being an implementation of threading, I would have expected the RaiseEvent of the worker to fire, and then the worker would continue, hence requiring me to pause the worker until the response is received. Instead however, the worker is held to wait for the code executed by the raise event to complete. It seems like method I am calling via the event call is actually on the worker thread used by the background worker, and I am surprised, since I expected to see it on the Main Thread which is where the mainform is running. Also surprisingly, there are no cross thread exceptions thrown. Can somebody please explain why this is not as I expect?

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• Thread testing for time

  - by DanielFH

  Hi there :) I'm making a thread for my application that's going to do an exit operation at a given time (only hours and minutes, day/month doesn't matter). Is this the right way to do it, and also the right way to test for time? I'm testing for a 24 hour clock by the way, not AM / PM. I'm then in another class going to call this something like new Thread(new ExitThread()).start(); public class ExitThread implements Runnable { @Override public void run() { Date date = new Date(System.currentTimeMillis()); String time = new SimpleDateFormat("HHmmss").format(date); int currentTime = Integer.parseInt(time); int exitTime = 233000; while(true) { try { Thread.sleep(10000); } catch (InterruptedException e) { e.printStackTrace(); } if(currentTime >= exitTime ) { // do exit operation here } } } Thanks. //D

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• ArrayBlockingQueue - How to "interrupt" a thread that is wating on .take() method

  - by bernhard

  I use an ArrayBlockingQueue in my code. Clients will wait untill an element becomes available: myBlockingQueue.take(); How can I "shutdown" my service in case no elements are present in the queue and the take() ist wating indefenitely for an element to become available? This method throws an InterruptedException. My question is, how can I "evoke" an Interrupted Exception so that take() will quit? (I also tought about notify(), but it seems I doesnt help here..) I know I could insert an special "EOF/QUIT" marker Element but is this really the only solution? UPDATE (regarding the comment, that points to another question with two solutions: one mentioned above using a "Poisoning Pill Object" and the second one is Thread.interrupt(): The myBlockingQueue.take() is used NOT in a Thread (extending Thread) but rather implements Runnable. It seems a Runnable does not provide the .interrupt() method? How could I interrupt the Runnable? Million Thanks Bernhard

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• How to implement cancellable worker thread

  - by Arnold Zokas

  Hi, I'm trying to implement a cancellable worker thread using the new threading constructs in System.Threading.Tasks namespace. So far I have have come up with this implementation: public sealed class Scheduler { private CancellationTokenSource _cancellationTokenSource; public System.Threading.Tasks.Task Worker { get; private set; } public void Start() { _cancellationTokenSource = new CancellationTokenSource(); Worker = System.Threading.Tasks.Task.Factory.StartNew( () => RunTasks(_cancellationTokenSource.Token), _cancellationTokenSource.Token ); } private static void RunTasks(CancellationToken cancellationToken) { while (!cancellationToken.IsCancellationRequested) { Thread.Sleep(1000); // simulate work } } public void Stop() { try { _cancellationTokenSource.Cancel(); Worker.Wait(_cancellationTokenSource.Token); } catch (OperationCanceledException) { // OperationCanceledException is expected when a Task is cancelled. } } } When Stop() returns I expect Worker.Status to be TaskStatus.Canceled. My unit tests have shown that under certain conditions Worker.Status remains set to TaskStatus.Running. Is this a correct way to implement a cancellable worker thread?

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• C# Thread issues

  - by Mike

  What I have going on is a listview being dynamically created from a previous button click. Then ti starts a background worker in which should clear out the listview and populate the iistview with new information every 30 seconds. I continously get: Cross-thread operation not valid: Control 'listView2' accessed from a thread other than the thread it was created on. private void watcherprocess1Updatelist() { listView2.Items.Clear(); string betaFilePath1 = @"C:\Alpha\watch1\watch1config.txt"; using (FileStream fs = new FileStream(betaFilePath1, FileMode.Open)) using (StreamReader rdr = new StreamReader((fs))) { while (!rdr.EndOfStream) { string[] betaFileLine = rdr.ReadLine().Split(','); using (WebClient webClient = new WebClient()) { string urlstatelevel = betaFileLine[0]; string html = webClient.DownloadString(urlstatelevel); File.AppendAllText(@"C:\Alpha\watch1\specificconfig.txt", html); } } }

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• Windows Service And Thread Programming .NET

  - by Raghu

  I have developed windows service to process files whose records will be stored in database. When windows service finds a file it creates a thread and assigns each file to one thread. I have not used Thread Pool. I wanted to know when windows service is stopped, then how to identify how many threads are running and whether they are complete. If all the threads are executed then windows service can be stopped successfully. Otherwis windows service should wait until all threads are executed or aborted. How to implement this.

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• Put Java Threading Class into a separate class

  - by erlord

  Consider following SWT code example: http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet151.java?view=co How can I separate the inline defined class? Thread thread = new Thread() { public void run() { ... } }; I want to define a separate class which updates the table just like it does here. How do I pass the list back to the table? Example code?

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• What exactly is a reentrant function?

  - by eSKay

  Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely on locks to singleton resources. Must not modify its own code (unless executing in its own unique thread storage) Must not call non-reentrant computer programs or routines. How is safely defined? If a program can be safely executed concurrently, does it always mean that it is reentrant? What exactly is the common thread between the six points mentioned that I should keep in mind while checking my code for reentrant capabilities? Also, Are all recursive functions reentrant? Are all thread-safe functions reentrant? Are all recursive and thread-safe functions reentrant? While writing this question, one thing comes to mind: Are the terms like reentrance and thread safety absolute at all i.e. do they have fixed concrete definations? For, if they are not, this question is not very meaningful. Thanks!

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• Is it okay to pass injected EntityManagers to EJB bean's helper classes and use it?

  - by Zwei steinen

  We have some JavaEE5 stateless EJB bean that passes the injected EntityManager to its helpers. Is this safe? It has worked well until now, but I found out some Oracle document that states its implementation of EntityManager is thread-safe. Now I wonder whether the reason we did not have issues until now, was only because the implementation we were using happened to be thread-safe (we use Oracle). @Stateless class SomeBean { @PersistenceContext private EntityManager em; private SomeHelper helper; @PostConstruct public void init(){ helper = new SomeHelper(em); } @Override public void business(){ helper.doSomethingWithEm(); } } Actually it makes sense.. If EntityManager is thread-unsafe, a container would have to do inercept business() this.em = newEntityManager(); business(); which will not propagate to its helper classes. If so, what is the best practice in this kind of a situation? Passing EntityManagerFactory instead of EntityManager?

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• Final enum in Thread's run() method

  - by portoalet

  Hi, Why is the Elvis elvis definition has to be final to be used inside the Thread run() method? Elvis elvis = Elvis.INSTANCE; // ----> should be final Elvis elvis = Elvis.INSTANCE elvis.sing(4); Thread t1 = new Thread( new Runnable() { @Override public void run() { elvis.sing(6); // --------> elvis has to be final to compile } } ); public enum Elvis { INSTANCE(2); Elvis() { this.x = new AtomicInteger(0); } Elvis(int x){ this.x = new AtomicInteger(x); } private AtomicInteger x = new AtomicInteger(0); public int getX() { return x.get(); } public void setX(int x) {this.x = new AtomicInteger(x);} public void sing(int x) { this.x = new AtomicInteger(x); System.out.println("Elvis singing.." + x); } }

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• Efficiently display file status when using background thread

  - by schmoopy

  How can i efficiently display the status of a file when using a background thread? For instance, lets say i have a 100MB file: when i do the code below via a thread (just as an example) it runs in about 1 min: foreach(byte b in file.bytes) { WriteByte(b, xxx); } But... if i want to update the user i have to use a delegate to update the UI from the main thread, the code below takes - FOREVER - literally i don't know how long im still waiting, ive created this post and its not even 30% done. int total = file.length; int current = 0; foreach(byte b in file.bytes) { current++; UpdateCurrentFileStatus(current, total); WriteByte(b, xxx); } public delegate void UpdateCurrentFileStatus(int cur, int total); public void UpdateCurrentFileStatus(int cur, int total) { // Check if invoke required, if so create instance of delegate // the update the UI if(this.InvokeRequired) { } else { UpdateUI(...) } }

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• How to interrupt a waiting C++0x thread?

  - by doublep

  I'm considering to use C++0x threads in my application instead of Boost threads. However, I'm not sure how to reimplement what I have with standard C++0x threads since they don't seem to have an interrupt() method. My current setup is: a master thread that manages work; several worker threads that carry out master's commands. Workers call wait() on at least two different condition variables. Master has a "timed out" state: in this case it tells all workers to stop and give whatever result they got by then. With Boost threads master just uses interrupt_all() on a thread group, which causes workers to stop waiting. In case they are not waiting at the moment, master also sets a bool flag which workers check periodically. However, in C++0x std::thread I don't see any replacement for interrupt(). Do I miss something? If not, how can I implement the above scheme so that workers cannot just sleep forever?

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• Async stream writing in a thread

  - by blez

  I have a thread in which I write to 2 streams. The problem is that the thread is blocked until the first one finishes writing (until all data is transferred on the other side of the pipe), and I don't want that. Is there a way to make it asynchronous? chunkOutput is a Dictionary filled with data from multiple threads, so the faster checking for existing keys is, the faster the pipe will write. void ConsumerMethod(object totalChunks) { while(true) { if (chunkOutput.ContainsKey(curChunk)) { if (outputStream != null && chunkOutput[curChunk].Length > 0) { outputStream.Write(chunkOutput[curChunk]); // <-- here it stops } ChunkDownloader.AppendData("outfile.dat", chunkOutput[curChunk], chunkOutput[curChunk].Length); curChunk++; if (curChunk >= (int) totalChunks) return; } Thread.Sleep(10); } }

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• How to buffer stdout in memory and write it from a dedicated thread

  - by NickB

  I have a C application with many worker threads. It is essential that these do not block so where the worker threads need to write to a file on disk, I have them write to a circular buffer in memory, and then have a dedicated thread for writing that buffer to disk. The worker threads do not block any more. The dedicated thread can safely block while writing to disk without affecting the worker threads (it does not hold a lock while writing to disk). My memory buffer is tuned to be sufficiently large that the writer thread can keep up. This all works great. My question is, how do I implement something similar for stdout? I could macro printf() to write into a memory buffer, but I don't have control over all the code that might write to stdout (some of it is in third-party libraries). Thoughts? NickB

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• iphone threading speed up startup of app

  - by BahaiResearch.com

  I have an app that must get data from the Sqlite database in order to display the first element to the User. I have created a domain object which wraps the DB access and is a thread safe singleton. Is this following strategy optimal to ensure the fastest load given the iPhone's file access and memory management capabilities in threaded apps: 1) In the AppDelegate's FinishedLaunching event the very first thing I do is create the domain singleton within a new thread. This will cause the domain object to go to Sqlite and get the data it needs without locking the UI thread. 2) I then call the standard Window methods to add the View and MakeKeyAndVisible etc. Is there an earlier stage in the AppDelegate where I should fire off the thread that creates the Domain Object and accesses Sqlite?

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• event vs thread programming on server side.

  - by AlxPeter

  We are planning to start a fairly complex web-portal which is expected to attract good local traffic and I've been told by my boss to consider/analyse node.js for the serve side. I think scalability and multi-core support can be handled with an Nginx or Cherokee up in the front. 1) Is this node.js ready for some serious/big business? 2) Does this 'event/asynchronous' paradigm on server side has the potential to support the heavy traffic and data operation ? considering the fact that 'everything' is being processed in a single thread and all the live connections would be lost if it got crashed (though its easy to restart). 3) What are the advantages of event based programming compared to thread based style ? or vice-versa. (I know of higher cost associated with thread switching but hardware can be squeezed with event model.) Following are interesting but contradicting (to some extent) papers:- 1) http://www.usenix.org/events/hotos03/tech/full_papers/vonbehren/vonbehren_html 2) http://pdos.csail.mit.edu/~rtm/papers/dabek:event.pdf

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• How to kill a thread immediately from another thread in java?

  - by Sara

  Hi, is there anyway to kill a thread or interrupt it immediately. Like in one of my thread, i call a method which takes time to execute (2-4 seconds). This method is in a while(boolean flag) block, so i can interrupt it from the main thread. But the problem is, if i interrupt it; it will wait till the executing loop is finished and then on next conditional check, it will stop execution. I want it to stop right then. Is there anyway to do this?

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• prevent linux thread from being interrupted by scheduler

  - by johnnycrash

  How do you tell the thread scheduler in linux to not interrupt your thread for any reason? I am programming in user mode. Does simply locking a mutex acomplish this? I want to prevent other threads in my process from being scheduled when a certain function is executing. They would block and I would be wasting cpu cycles with context switches. I want any thread executing the function to be able to finish executing without interruption even if the threads' timeslice is exceeded.

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• c++ simple start a function with its own thread

  - by user1397417

  i had once had a very simple one or two line code that would start a function with its own thread and continue running until application closed, c++ console app. lost the project it was in, and remember it was hard to find. cant find it online now. most example account for complicated multithreading situations. but i just need to open this one function in its own thread. hopefully someone knows what im talking about, or a similar solution. eg. start void abc in its own thread, no parameters

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• Referenced assembly won't load in new thread on IIS 7

  - by DanielC

  I have a process in which a user uploads a file to a web site where the file is then processed and uploaded into the database. The process of validating the file could take several minutes so as soon as the file is uploaded I create a new thread and I do my processing on this second thread. This works great on my local machine but doesn't work at all on my IIS 7 test server. After some investigating I found the problem is that the process is trying to load a reference to Castle and it can't find the DLL. I have a copy of Castle DLLs in my bin and it works elsewhere in my app. I ran Fuslog and discovered that it is trying to load castle from the wrong location. It is trying to load from c:/windows/system32/inetsrv/. It appears that under IIS 7 the second thread is executing in a different context or something. So the question is what can I do to get it to find Castle in the application BIN folder?

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