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  • Pattern for iPhone background loading during init?

    - by Rob S.
    Hi everyone, I'm currently kicking off a background thread to do some REST queries in my app delegate's didFinishLaunchingWithOptions. This thread creates some objects and populates the model as the rest of the app continues to load (because I don't block, and didFinishLaunchingWithOptions returns YES). I also put up a loading UIViewController 'on top' of the main view that I tear down after the background initialization is complete. My problem is that I need to notify the first view (call it the Home view) that the model is ready, and that it should populate itself. The trick is that the background download could have finished before Home.viewDidAppear is called, or any of the other Home.initX methods. I'm having difficulty synchronizing all of this and I've thought about it long enough that it feels like I'm barking up the wrong tree. Are there any patterns here for this sort of thing? I'm sure other apps start by performing lengthy operations with loading screens :) Thanks!

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  • threading.Event wait function not signaled when subclassing Process class

    - by user1313404
    For following code never gets past the wait function in run. I'm certain I'm doing something ridiculously stupid, but since I'm not smart enough to figure out what, I'm asking. Any help is appreciated. Here is the code: import threading import multiprocessing from multiprocessing import Process class SomeClass(Process): def __init__(self): Process.__init__(self) self.event = threading.Event() self.event.clear() def continueExec(self): print multiprocessing.current_process().name print self print "Set:" + str(self.event.is_set()) self.event.set() print "Set:" + str(self.event.is_set()) def run(self): print "I'm running with it" print multiprocessing.current_process().name self.event.wait() print "I'm further than I was" print multiprocessing.current_process().name self.event.clear() def main(): s_list = [] for t in range(3): s = SomeClass() print "s:" + str(s) s_list.append(s) s.start() raw_input("Press enter to send signal") for t in range(3): print "s_list["+str(t)+"]:" + str(s_list[t]) s_list[t].continueExec() raw_input("Press enter to send signal") for t in range(3): s_list[t].join() print "All Done" if __name__ == "__main__": main()

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  • How does jQuery have asynchronous functions?

    - by Sam.Rueby
    I'm surprised I can't find a clear answer to this. So, in jQuery, you can do this: $(someElements).fadeOut(1000); $(someElements).remove(); Which, will start a fadeOut animation, but before it finishes executing in the 1 second duration, the elements are removed from the DOM. But how is this possible? I keep reading the JavaScript is single threaded. ( Is javascript guaranteed to be single-threaded? ) This question is not "How do I fix this?" I know I can do either: $(someElements).fadeOut(1000).promise().done(function() { $(someElements).remove();});, or even better:$(someElements).fadeOut(1000, function() { $(this).remove(); } ); What I don't understand is how JavaScript runs in a "single thread" but I'm able to use these jQuery functions that execute asynchronously and visibly see the DOM change in different places at the same time. How does it work?

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  • Cross Thread problem C#

    - by Frederik Witte
    Hello people - I got this code (lg_log is a listbox, and i want it to log the start_server.bat) Here is the code i got: public void bt_play_Click(object sender, EventArgs e) { lg_log.Items.Add("Starting Mineme server .."); string directory = Directory.GetCurrentDirectory(); var info = new ProcessStartInfo(directory + @"\start_base.bat") {UseShellExecute = false, RedirectStandardOutput = true, CreateNoWindow = true, WorkingDirectory = directory + @"\Servers\Base"}; var proc = new Process { StartInfo = info, EnableRaisingEvents = true }; proc.OutputDataReceived += (obj, args) => { if (args.Data != null) { lg_log.Items.Add(args.Data); } }; proc.Start(); proc.BeginOutputReadLine(); lg_log.Items.Add("Server is now running!"); proc.WaitForExit(); } When i run this, i'll get an error .. Anybody can help me? I'll rate the answer up! :D Edit: The error i get is this: System.InvalidOperationException Hope it helps :) The error comes at the lg_log.Items.Add(args.Data); code line

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  • C#: Populating a UI using separate threads.

    - by Andrew
    I'm trying to make some sense out of an application Ive been handed in order to track down the source of an error. Theres a bit of code (simplified here) which creates four threads which in turn populate list views on the main form. Each method gets data from the database and retrieves graphics from a resource dll in order to directly populate an imagelist and listview. From what Ive read on here (link) updating UI elements from any thread other than the UI thread should not be done, and yet this appears to work? Thread t0 = new Thread(new ThreadStart(PopulateListView1)); t0.IsBackground = true; t0.Start(); Thread t1 = new Thread(new ThreadStart(PopulateListView2)); t1.Start(); Thread t2 = new Thread(new ThreadStart(PopulateListView3)); t2.Start(); Thread t3 = new Thread(new ThreadStart(PopulateListView4)); t3.Start(); The error itself is a System.InvalidOperationException "Image cannot be added to the ImageList." which has me wondering if the above code is linked in some way. Iis this method of populating the UI recommended and if not what are the possible complications resulting from it?

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  • OGNL thread safety

    - by Dewfy
    I'm going to reuse OGNL library out of Struts2 scope. I have rather large set of formulas, that is why I would like to precompile all of them: Ognl.parseExpression(expressionString); But I'm not sure if precompiled expression can be used in multi-thread environment. Does anybody knows if it can be used?

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  • WM6x IMAPIAdviseSink::OnNotify threading issues

    - by violet313
    specifically WM6x, winCE5x Now my current understanding from trawling the msdn etal is that the IMAPIAdviseSink::OnNotify callback can be made from any old thread; from (ce)mapi or perhaps even from a third-party service provider. Under WM6x, i cannot seem to coax an in-thread response by invoking HrThisThreadAdviseSink, since while this function is declared in mapiutil.h, a definition appears not to exist (in cemapi.lib or wherever??) ~But i notice that all the OnNotify callbacks i receive derive from windows messages that i am receiving on my thread (=looks to me like an in-thread implementation in any case under cemapi)... So, can anyone confirm that this is infact always the case -or am i just getting lucky right now? ah, i should add that my advise source is IMAPISession::Advise erm i should also say that i might have cross-posted this on the msdn forum -but they're mostly numptys over there,,

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  • Noise with multi-threaded raytracer

    - by herber88
    This is my first multi-threaded implementation, so it's probably a beginners mistake. The threads handle the rendering of every second row of pixels (so all rendering is handled within each thread). The problem persists if the threads render the upper and lower parts of the screen respectively. Both threads read from the same variables, can this cause any problems? From what I've understood only writing can cause concurrency problems... Can calling the same functions cause any concurrency problems? And again, from what I've understood this shouldn't be a problem... The only time both threads write to the same variable is when saving the calculated pixel color. This is stored in an array, but they never write to the same indices in that array. Can this cause a problem? Multi-threaded rendered image (Spam prevention stops me from posting images directly..) Ps. I use the exactly same implementation in both cases, the ONLY difference is a single vs. two threads created for the rendering.

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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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  • how to emulate thread local storage at user space in C++ ?

    - by vprajan
    I am working on a mobile platform over Nucleus RTOS. It uses Nucleus Threading system but it doesn't have support for explicit thread local storage i.e, TlsAlloc, TlsSetValue, TlsGetValue, TlsFree APIs. The platform doesn't have user space pthreads as well. I found that __thread storage modifier is present in most of the C++ compilers. But i don't know how to make it work for my kind of usage. How does __thread keyword can be mapped with explicit thread local storage? I read many articles but nothing is so clear for giving me the following basic information will __thread variable different for each thread ? How to write to that and read from it ? does each thread has exactly one copy of the variable ? following is the pthread based implementation: pthread_key_t m_key; struct Data : Noncopyable { Data(T* value, void* owner) : value(value), owner(owner) {} int* value; }; inline ThreadSpecific() { int error = pthread_key_create(&m_key, destroy); if (error) CRASH(); } inline ~ThreadSpecific() { pthread_key_delete(m_key); // Does not invoke destructor functions. } inline T* get() { Data* data = static_cast<Data*>(pthread_getspecific(m_key)); return data ? data->value : 0; } inline void set(T* ptr) { ASSERT(!get()); pthread_setspecific(m_key, new Data(ptr, this)); } How to make the above code use __thread way to set & get specific value ? where/when does the create & delete happen? If this is not possible, how to write custom pthread_setspecific, pthread_getspecific kind of APIs. I tried using a C++ global map and index it uniquely for each thread and retrieved data from it. But it didn't work well.

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  • Unload event for the default AppDomain?

    - by Zor
    Hi, I need to have an event fired whenever any AppDomain unloads - including the default one of the process. The problem with AppDomain.DomainUnload is that it only fires for non-default AppDomains. Furthermore, AppDomain.ProcessExit has limited execution time, which I cannot rely on. Any suggestions as to how I can achieve this would be greatly appreciated! (Alternatively, having an event fired when a background thread (Thread.IsBackground == True) works too.) Thanks in advance.

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  • C++ thread to separate process

    - by silverbandit91
    Is there any way I can have a thread branch off into its own independent process? I know there's the CreateProcess function but as far as I can tell, you can only run external applications with it. Is what I'm asking for at all possible?

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  • Swing modal dialog refuses to close - sometimes!

    - by Zarkonnen
    // This is supposed to show a modal dialog and then hide it again. In practice, // this works about 75% of the time, and the other 25% of the time, the dialog // stays visible. // This is on Ubuntu 10.10, running: // OpenJDK Runtime Environment (IcedTea6 1.9) (6b20-1.9-0ubuntu1) // This always prints // setVisible(true) about to happen // setVisible(false) about to happen // setVisible(false) has just happened // even when the dialog stays visible. package modalproblemdemo; import java.awt.Frame; import javax.swing.JDialog; import javax.swing.SwingUtilities; public class Main { public static void main(String[] args) { final Dialogs d = new Dialogs(); new Thread() { @Override public void run() { d.show(); d.hide(); } }.start(); } static class Dialogs { final JDialog dialog; public Dialogs() { dialog = new JDialog((Frame) null, "Hello World", /*modal*/ true); dialog.setSize(400, 200); } public void show() { SwingUtilities.invokeLater(new Runnable() { public void run() { dialog.setLocationRelativeTo(null); System.out.println("setVisible(true) about to happen"); dialog.setVisible(true); }}); } public void hide() { SwingUtilities.invokeLater(new Runnable() { public void run() { System.out.println("setVisible(false) about to happen"); dialog.setVisible(false); System.out.println("setVisible(false) has just happened"); }}); } } }

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  • Proper thread termination in multi-threaded C# application

    - by Brian
    I have what I think is a rather complex problem. I have a C# application that utilizes a plug-in architecture using reflection. The application loads plug-in dlls and the user is able to enable/disable them. When a plug-in is enabled, the main app starts a thread to run the plug-in in. In many cases the plug-in may have multiple threads of its own. When I want to disable a plug-in I am calling Thread.Abort(). This seems to kill the initial thread that was created for the plug-in, but any additional threads that the plug-in created continue running. Is there a better way to stop all of the associated plug-in's threads along with the main thread? Thanks.

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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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  • Millisecond-Accurate Scheduling of Future Events in C++/CLI

    - by A Grad Student at a University
    I need to create a C++/CLI mixed assembly that can schedule future calls into a native DLL with millisecond accuracy. This will, of course, mean setting a timer (what kind?) for a millisecond or three beforehand, then spinning until the moment and calling the native DLL function. Based on what I've read, I would guess that the callback that the timer calls will need to be native to make sure there are no thunks or GC to delay handling the timer callback. Will the entire thread or process need to be native and CLR-free, though, or can this be done just as accurately with #pragma unmanaged or setting one file of the assembly to compile as native? If so, how? If there is indeed no way to do this in mixed-mode C++/CLI, what would be the easiest way to set up an app/thread (ie, DLL or exe?) to handle it and to get the data back and forth between the native and managed threads/apps?

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  • Basic QT Event handling / Threading questions ?

    - by umanga
    Greetings , I am new to QT (4.6) and have some basic questions regarding its event mechanism.I come from Swing background so I am trying to compare it with QT. 1) Does Event-processing-loop run in seperate thread? (like EventDispatch thread in Swing) ? 2) If we open several 'QMainWindow' do they run in several threads? 3) Whats the best way to run an intensive process in a seperate thread? (like SwingWorker in Swing ? ) 4) If intesive-process runs in a seperate thread ,is it possible to call UI methods like update(),repaint() from that process? thanks in advance.

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  • Are Thread.stop and friends ever safe in Java?

    - by Stephen C
    The stop(), suspend(), and resume() in java.lang.Thread are deprecated because they are unsafe. The Sun recommended work around is to use Thread.interrupt(), but that approach doesn't work in all cases. For example, if you are call a library method that doesn't explicitly or implicitly check the interrupted flag, you have no choice but to wait for the call to finish. So, I'm wondering if it is possible to characterize situations where it is (provably) safe to call stop() on a Thread. For example, would it be safe to stop() a thread that did nothing but call find(...) or match(...) on a java.util.regex.Matcher? (If there are any Sun engineers reading this ... a definitive answer would be really appreciated.) EDIT: Answers that simply restate the mantra that you should not call stop() because it is deprecated, unsafe, whatever are missing the point of this question. I know that that it is genuinely unsafe in the majority of cases, and that if there is a viable alternative you should always use that instead. This question is about the subset cases where it is safe. Specifically, what is that subset?

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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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  • Thread Question

    - by Polaris
    I have method which create background thread to make some action. In this background thread I create object. But this object while creating in runtime give me an exception : The calling thread must be STA, because many UI components require this. I know that I must use Dispatcher to make reflect something to UI. But in this case I just create an object and dont iteract with UI. This is my code: public void SomeMethod() { BackgroundWorker worker = new BackgroundWorker(); worker.DoWork += new DoWorkEventHandler(Background_Method); worker.RunWorkerAsync(); } void Background_Method(object sender, DoWorkEventArgs e) { TreeView tv = new TreeView(); } How can I create objects in background thread? I use WPF application

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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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