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Search found 1455 results on 59 pages for 'threading'.

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  • Should an NSLock instance be "global"?

    - by Alex Reynolds
    Should I make a single NSLock instance in the application delegate, to be used by all classes? Or is it advisable to have each class instantiate its own NSLock instance as needed? Would the locking work in the second case, if I, for example, had access to a managed object context that is spread across two view controllers?

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  • How to show that the double-checked-lock pattern with Dictionary's TryGetValue is not threadsafe in

    - by Amir
    Recently I've seen some C# projects that use a double-checked-lock pattern on a Dictionary. Something like this: private static readonly object _lock = new object(); private static volatile IDictionary<string, object> _cache = new Dictionary<string, object>(); public static object Create(string key) { object val; if (!_cache.TryGetValue(key, out val)) { lock (_lock) { if (!_cache.TryGetValue(key, out val)) { val = new object(); // factory construction based on key here. _cache.Add(key, val); } } } return val; } This code is incorrect, since the Dictionary can be "growing" the collection in _cache.Add() while _cache.TryGetValue (outside the lock) is iterating over the collection. It might be extremely unlikely in many situations, but is still wrong. Is there a simple program to demonstrate that this code fails? Does it make sense to incorporate this into a unit test? And if so, how?

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  • .NET Thread.Abort again

    - by hoodoos
    Again I want to talk about safety of the Thread.Abort function. I was interested to have some way to abort operations which I can't control really and don't want actually, but I want to have my threads free as soon as possible to prevent thread thirsty of my application. So I wrote some test code to see if it's possible to use Thread.Abort and have the aborting thread clean up resources propertly. Here's code: int threadRunCount = 0; int threadAbortCount = 0; int threadFinallyCount = 0; int iterations = 0; while( true ) { Thread t = new Thread( () => { threadRunCount++; try { Thread.Sleep( Random.Next( 45, 55 ) ); } catch( ThreadAbortException ) { threadAbortCount++; } finally { threadFinallyCount++; } } ); t.Start(); Thread.Sleep( 45 ); t.Abort(); iterations++; } So, so far this code worked for about 5 mins, and threadRunCount was always equal to threadFinally and threadAbort was somewhat lower in number, because some threads completed with no abort or probably got aborted in finally. So the question is, do I miss something?

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  • Filling SWT table object using a separated thread class ...

    - by erlord
    Hi all I've got a code snippet by the swt team that does exactly what I need. However, there is a part I want to separate into another class, in particular, the whole inline stuff. In response to my former question, it has been suggested that Callable should be used in order to implement threaded objects. It is suggested to make use of an implementation of runnable or better callable, since I do need some kind of return. However, I don't get it. My problems are: In the original code, within the inline implementation of the method run, some of the parents objects are called. How would I do this when the thread is separated? Pass the object via the C'tor's parameter? In the original code, another runnable object is nested within the runnable implementation. What is it good for? How to implement this when having separated the code? Furthermore, this nested runnable again calls objects created by the main method. Please, have mercy with me, but I am still quite a beginner and my brain is near collapsing :-( All I want is to separate all the threaded stuff into another class and make the program do just the same thing as it already does. Help please! Again thank you very much in advance for any useful suggestions, hints, examples etc... Regs Me

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  • How to make an HTTP request in a separate thread with timeout?

    - by Vitaly
    Hi, I haven't programmed in Delphi for a while and frankly didn't think I'll ever have to but... Here I am, desperately trying to find some information on the matter and it's so scarce nowadays, I can't find anything. So maybe you guys could help me out. Currently my application uses Synapse library to make HTTP calls, but it doesn't allow for setting a timeout. Usually, that's not a big problem, but now I absolutely must to have a timeout to handle any connectivity issues nicely. What I'm looking for, is a library (synchronous or not) that will allow making HTTP requests absolutely transparent for the user with no visible or hidden delays. I can't immediately kill a thread right now, and with possibility of many frequent requests to the server that is not responding, it's no good.

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  • What does flushing thread local memory to global memory mean?

    - by Jack Griffith
    Hi, I am aware that the purpose of volatile variables in Java is that writes to such variables are immediately visible to other threads. I am also aware that one of the effects of a synchronized block is to flush thread-local memory to global memory. I have never fully understood the references to 'thread-local' memory in this context. I understand that data which only exists on the stack is thread-local, but when talking about objects on the heap my understanding becomes hazy. I was hoping that to get comments on the following points: When executing on a machine with multiple processors, does flushing thread-local memory simply refer to the flushing of the CPU cache into RAM? When executing on a uniprocessor machine, does this mean anything at all? If it is possible for the heap to have the same variable at two different memory locations (each accessed by a different thread), under what circumstances would this arise? What implications does this have to garbage collection? How aggressively do VMs do this kind of thing? Overall, I think am trying to understand whether thread-local means memory that is physically accessible by only one CPU or if there is logical thread-local heap partitioning done by the VM? Any links to presentations or documentation would be immensely helpful. I have spent time researching this, and although I have found lots of nice literature, I haven't been able to satisfy my curiosity regarding the different situations & definitions of thread-local memory. Thanks very much.

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  • strange behavior in python

    - by fsm
    The tags might not be accurate since I am not sure where the problem is. I have a module where I am trying to read some data from a socket, and write the results into a file (append) It looks something like this, (only relevant parts included) if __name__ == "__main__": <some init code> for line in file: t = Thread(target=foo, args=(line,)) t.start() while nThreads > 0: time.sleep(1) Here are the other modules, def foo(text): global countLock, nThreads countLock.acquire() nThreads += 1 countLock.release() """connect to socket, send data, read response""" writeResults(text, result) countLock.acquire() nThreads -= 1 countLock.release() def writeResults(text, result): """acquire file lock""" """append to file""" """release file lock""" Now here's the problem. Initially, I had a typo in the function 'foo', where I was passing the variable 'line' to writeResults instead of 'text'. 'line' is not defined in the function foo, it's defined in the main block, so I should have seen an error, but instead, it worked fine, except that the data was appended to the file multiple times, instead of being written just once, which is the required behavior, which I got when I fixed the typo. My question is, 1) Why didn't I get an error? 2) Why was the writeResults function being called multiple times?

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  • [Java] - Problem having my main thread sleeping

    - by Chris
    I'm in a Java class and our assignment is to let us explore threads in Java. So far so good except for this one this one problem. And I believe that could be because of my lack of understanding how Java threads work at the moment. I have the main thread of execution which spawns new threads. In the main thread of execution in main() I am calling Thread.sleep(). When I do I get an Unhandled exception type InterruptedException. I am unsure of why I am getting this? I thought this was because I needed a reference to the main thread so I went ahead and made a reference to it via Thread.currentThread(). Is this not the way to have the thread sleep? What I need to do is have the main thread wait/sleep/delay till it does it required work again. Any help would be much appreciated.

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  • How to know if all the Thread Pool's thread are already done with its tasks?

    - by mcxiand
    I have this application that will recurse all folders in a given directory and look for PDF. If a PDF file is found, the application will count its pages using ITextSharp. I did this by using a thread to recursively scan all the folders for pdf, then if then PDF is found, this will be queued to the thread pool. The code looks like this: //spawn a thread to handle the processing of pdf on each folder. var th = new Thread(() => { pdfDirectories = Directory.GetDirectories(pdfPath); processDir(pdfDirectories); }); th.Start(); private void processDir(string[] dirs) { foreach (var dir in dirs) { pdfFiles = Directory.GetFiles(dir, "*.pdf"); processFiles(pdfFiles); string[] newdir = Directory.GetDirectories(dir); processDir(newdir); } } private void processFiles(string[] files) { foreach (var pdf in files) { ThreadPoolHelper.QueueUserWorkItem( new { path = pdf }, (data) => { processPDF(data.path); } ); } } My problem is, how do i know that the thread pool's thread has finished processing all the queued items so i can tell the user that the application is done with its intended task?

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  • How do you call a generic method on a thread?

    - by cw
    How would I call a method with the below header on a thread? public void ReadObjectAsync<T>(string filename) { // Can't use T in a delegate, moved it to a parameter. ThreadStart ts = delegate() { ReadObjectAcync(filename, typeof(T)); }; Thread th = new Thread(ts); th.IsBackground = true; th.Start(); } private void ReadObjectAcync(string filename, Type t) { // HOW? } public T ReadObject<T>(string filename) { // Deserializes a file to a type. }

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  • Using SetThreadAffinityMask function imported from kernel32.dll in C # code.

    - by DotNetBeginner
    I am trying to set Thread Affinity using SetThreadAffinityMask function imported from kernel32.dll in C # code of mine. This is how I import SetThreadAffinityMask function from "kernel32.dll" in my C# .net code [DllImport("kernel32.dll")] static extern IntPtr SetThreadAffinityMask(IntPtr hThread, IntPtr dwThreadAffinityMask); I am creating 3 threads Thread t1=new Thread(some delegate); Thread t2=new Thread(some delegate); Thread t3=new Thread(some delegate); I wish to set Thread affinity for t1,t2 & t3 for which I am using SetThreadAffinityMask function. But I am not getting how to pass parameters to this function. SetThreadAffinityMask takes two parameters 1. HANDLE hThread 2. DWORD_PTR dwThreadAffinityMask Please help me in using SetThreadAffinityMask function in C# Thanks in advance !

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  • What is difference between Thread Affinity and Process affinity ?

    - by DotNetBeginner
    What is difference between Thread Affinity and Process affinity ? If I have two Threads and I have duel core machine then is it possible to run these two threads parallely on the two cores ? If I use processor affinity Mask then I can control execution of a process on the cores but when I have to run threads on a particular core how can I make these threads core specific ? A very simple example will be appreciated.

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  • Will thread.join() block other clients also?

    - by maxp
    In an asp.net web application, say everytime the user makes the request, and the page loads, a thread is fired off that uses thread.join() to block execution until it's finished. Say this thread takes 10 seconds to complete. Does this mean that if 5 totally seperate users make a request to this page, mere miliseconds after the last, does this mean the last user is going to wait 50 seconds to finish their request? Or is each client request threaded?

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  • Python sock.listen(...)

    - by Ian
    All the examples I've seen of sock.listen(5) in the python documentation suggest I should set the max backlog number to be 5. This is causing a problem for my app since I'm expecting some very high volume (many concurrent connections). I set it to 200 and haven't seen any problems on my system, but was wondering how high I can set it before it causes problems.. Anyone know?

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  • Monitor.Wait, Pulse - When worker thread should conditionally behave as an actual worker thread

    - by Griever
    My particular scenario: - Main thread starts a worker thread. - Main thread needs to block itself until either worker thread is completed (yeah funny) or worker thread itself informs main thread to go on Alright, so what I did in main thread: wokerThread.Start(lockObj); lock(lockObj) Monitor.Wait(lockObj); Somewhere in worker thread: if(mainThreadShouldGoOn) lock(lockObj) Monitor.Pulse(lockObj); Also, at the end of worker thread: lock(lockObj) Monitor.Pulse(lockObj); So far, it's working perfect. But is it a good solution? Is there a better one?

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  • Need help understanding _set_security_error_handler()

    - by Emil D
    So , I've been reading this article: http://msdn.microsoft.com/en-us/library/aa290051%28VS.71%29.aspx And I would like to define my custom handler.However, I'm not sure I understand the mechanics well.What happens after a call is made to the user-defined function ( e.g. the argument of _set_security_error_handler() ) ? Does the program still terminate afterward ? If that is the case, is it possible to terminate only the current thread(assuming that it is not the main thread of the application).AFAIK, each thread has its own stack , so if the stack of a thread gets corrupted, the rest of the application shouldn't be affected. Finally, if it is indeed possible to only terminate the current thread of execution, what potential problems could such an action cause? I'm trying to do all this inside an unmanaged C++ dll that I would like to use in my C# code.

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  • How to write async background workers that work on WPF flowdocument

    - by iBe
    I'm trying to write a background worker that processes a flowdocument. I can't access the properties of flowdocument objects because of the thread verification. I tried to serialize the document and loaded it on the worker thread which actually solved the thread verfication issue. However, once the processing is complete I also need to use things like TextPointer objects. Those objects now point to a objects in the copy not the original. Can anyone suggest the best way to approach such background processing in WPF?

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  • Requesting information from the user inside a GTK main loop

    - by Victor Stanciu
    Hello, I am learning Python by building a simple PyGTK application that fetches data from some SVN repositories, using pysvn. The pysvn Client has a callback you can specify that it calls when Subversion needs authentication information for a repository. When that happens, I would like to open a dialog to ask the user for the credentials. The problem is, it seems the callback is called inside the GTK main loop, so it's basically called on every tick. Is there a way to prevent this? Perhaps by opening the dialog in a new thread? But then how do I return the tuple with the user data to the callback so it can return it to the pysvn.Client?

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  • In app purchase on iphone.: How to receive your available products *before* someone may be able to b

    - by Thorsten S.
    Currently I am loading my supported products from a plist and after that I send a SKProductsRequest to guarantee that my SKProducts are still valid. So I set up the request, start it and get the response in: (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response Now, so far all functions correctly. Problem: From calling the request until receiving the response it may last several seconds. Until that my app is already loaded and the user may be able to choose and buy a product. But because no products have been received, the available products are not in sync with the validated products - unlikely, but possible error. So my idea is to wait until the data is loaded and only continue when the list is validated. (Just a few seconds waiting...). I have a singleton instance managing all products. + (MyClass *) sharedInstance { if (!sharedInstance) sharedInstance = [MyClass new]; // Now wait until we have our data [condition lock]; while (noEntriesYet) // is yes at begin [condition wait]; [condition unlock]; return sharedInstance; } - productsRequest: didReceiveResponse: { [condition lock]; // I have my data noEntriesYet = false; [condition signal]; [condition unlock]; } Problem: The app freezes. Everything works fine if didReceiveResponse is completed before the sharedInstance is queried. There are different threads, the lock is working if wait is reached during didReceiveResponse, everything fine. But if not, didReceiveResponse is never called even if the request was sent. The lock is released, everything looks ok. I have tried to send the product request in a separate NSThread, with NSOperationQueue...without avail. Why ? What is happening ? How to solve the problem ?

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  • Using a JMS Session from different threads

    - by Evan
    From the javadoc for Session it states: A Session object is a single-threaded context for producing and consuming messages. So I understand that you shouldn't use a Session object from two different threads at the same time. What I'm unclear on is if you could use the Session object (or children such as a Queue) from a different thread than the one it created. In the case I'm working on, I'm considering putting my Session objects into a pool of available sessions that any thread could borrow from, use, and return to the pool when it is finished with it. Is this kosher? (Using ActiveMQ BTW, if that impacts the answer at all.)

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  • conceptual question : what do performSelectorOnMainThread do?

    - by hib
    Hello all, I just come across this strange situation . I was using the technique of lazy image loading from apple examples . when I was used the class in my application it gave me topic to learn but don't what was actually happening there . So here goes the scenario : I think everybody has seen the apple lazytableimagesloading . I was reloading my table on finishing the parsing of data : - (void)didFinishParsing:(NSMutableArray *)appList { self.upcomingArray = [NSMutableArray arrayWithArray:loadedApps]; // we are finished with the queue and our ParseOperation [self.upcomingTableView reloadData]; self.queue = nil; // we are finished with the queue and our ParseOperation } but as a result the the connection was not starting and images were not loading . when I completely copy the lazyimageloading and I replaced the above code with the following code it works fine - (void)didFinishParsing:(NSMutableArray *)appList { [self performSelectorOnMainThread:@selector(handleLoadedApps:) withObject:appList waitUntilDone:NO]; self.queue = nil; // we are finished with the queue and our ParseOperation } So I want to know what is the concept behind this . Please let me know if you can not understand the question or details are not enough because I desperately want to know why it is like this ?

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  • Why .NET does not allow cross-thread operations?

    - by RHaguiuda
    This question is not about what is a cross-thread operation, and how to avoid it, but why internal mechanics of .NET framework does not allow a cross-thread operation. I can`t understand why a SerialPort DataReceived event cannot update a simple text box on my form and why using delegates this is possible?

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  • Stream writing lags my GUI

    - by blez
    I have a thread that dequeues data from a queue and write it to another application's STDIN. I'm using Stream, but with .Write and even .BeginWrite, when I send 1mb chunks to the second app, my GUI gets laggy for ~1sec. Why?

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