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  • Update C# Chart using BackgroundWorker

    - by Mark
    I am currently trying to update a chart which is on my form to the background worker using: bwCharter.RunWorkerAsync(chart1); Which runs: private void bcCharter_DoWork(object sender, DoWorkEventArgs e) { System.Windows.Forms.DataVisualization.Charting.Chart chart = null; // Convert e.Argument to chart //.. // Converted.. chart.Series.Clear(); e.Result=chart; setChart(c.chart); } private void setChart(System.Windows.Forms.DataVisualization.Charting.Chart arg) { if (chart1.InvokeRequired) { chart1.Invoke(new MethodInvoker(delegate { setChart(arg); })); return; } chart1 = arg; } However, at the point of clearing the series, an exception is thrown. Basically, I want to do a whole lot more processing after clearing the series, which slows the GUI down completely - so wanted this in another thread. I thought that by passing it as an argument, I should be safe, but apparently not! Interestingly, the chart is on a tab page. I can run this over and over if the tabpage is in the background, but if I run this, look at the chart, hide it again, and re-run, it throws the exception. Obviously, it throws if the chart is in the foreground as well. Can anyone suggest what I can do differently? Thanks!

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  • {DCC Warning} W1036 Variable '$frame' might not have been initialized?

    - by Gad D Lord
    Any ideas why I get this warning in Delphi XE: [DCC Warning] Form1.pas(250): W1036 Variable '$frame' might not have been initialized procedure TForm1.Action1Execute(Sender: TObject); var Thread: TThread; begin ... Thread := TThread.CreateAnonymousThread( procedure{Anonymos}() procedure ShowLoading(const Show: Boolean); begin /// <------------- WARNING IS GIVEN FOR THIS LINE (line number 250) Thread.Synchronize(Thread, procedure{Anonymous}() begin ... Button1.Enabled := not Show; ... end ); end; var i: Integer; begin ShowLoading(true); try Thread.Synchronize(Thread, procedure{Anonymous}() begin ... // some UI updates end Thread.Synchronize(Thread, procedure{Anonymous}() begin ... // some UI updates end ); finally ShowLoading(false); end; end ).NameThread('Some Thread Name'); Thread.Start; end; I do not have anywhere in my code a variable names frame nor $frame. I am even not sure how $frame with $ sign can be a valid identifier. Smells like compiler magic to me. PS: Of course the real life xosw is having other than Form1, Button1, Action1 names.

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  • How to re-use a thread in Java ?

    - by David
    I am a building a console Sudoku Solver where the main objective is raw speed. I now have a ManagerThread that starts WorkerThreads to compute the neibhbors of each cell. So one WorkerThread is started for each cell right now. How can I re-use an existing thread that has completed its work? The Thread Pool Pattern seems to be the solution, but I don't understand what to do to prevent the thread from dying once its job has been completed. ps : I do not expect to gain much performance for this particular task, just want to experiment how multi-threading works before applying it to the more complex parts of the code. Thanks

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  • SwingWorker in Java (beginner question)

    - by Malachi
    I am relatively new to multi-threading and want to execute a background task using a Swingworker thread - the method that is called does not actually return anything but I would like to be notified when it has completed. The code I have so far doesn't appear to be working: private void crawl(ActionEvent evt) { try { SwingWorker<Void, Void> crawler = new SwingWorker<Void, Void>() { @Override protected Void doInBackground() throws Exception { Discoverer discover = new Discoverer(); discover.crawl(); return null; } @Override protected void done() { JOptionPane.showMessageDialog(jfThis, "Finished Crawling", "Success", JOptionPane.INFORMATION_MESSAGE); } }; crawler.execute(); } catch (Exception ex) { JOptionPane.showMessageDialog(this, ex.getMessage(), "Exception", JOptionPane.ERROR_MESSAGE); } } Any feedback/advice would be greatly appreciated as multi-threading is a big area of programming that I am weak in.

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  • Writing a search engine

    - by wvd
    Hello all, The title might be a bit misleading, but I couldn't figure out a better title. I'm writing a simple search engine which will search on several sites for the specific domain. To be concrete: I'm writing a search engine for hardstyle livesets/aftermovies/tracks. To do I will search on the sites who provide livesets, tracks, and such. The problem here is speed, I need to pass the search query to 5-7 sites, get the results and then use my own algorithm to display the results in a sorted order. I could just "multithread" it, but it's easier said then done so I have a few questions. What would be the best solution to this problem? Should I just multithread/process this application, so I'm going to get a bit of speed-up? Are there any other solutions or I am doing something really wrong? Thanks, William van Doorn

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  • Kill a Perl system call after a timeout

    - by Fergal
    I've got a Perl script I'm using for running a file processing tool which is started using backticks. The problem is that occasionally the tool hangs and It needs to be killed in order for the rest of the files to be processed. Whats the best way best way to apply a timeout after which the parent script will kill the hung process? At the moment I'm using: foreach $file (@FILES) { $runResult = `mytool $file >> $file.log`; } But when mytool hangs after n seconds I'd like to be able to kill it and continue to the next file.

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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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  • 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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  • Java multi-threading - what is the best way to monitor the activity of a number of threads?

    - by MalcomTucker
    I have a number of threads that are performing a long runing task. These threads themselves have child threads that do further subdivisions of work. What is the best way for me to track the following: How many total threads my process has created What the state of each thread currently is What part of my process each thread has currently got to I want to do it in as efficient a way as possible and once threads finish, I don't want any references to them hanging around becasuse I need to be freeing up memory as early as possible. Any advice?

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  • Thread Proc for an instancable class?

    - by user146780
    Basically I have a class and it is instincable (not static). Basically I want the class to be able to generate its own threads and manage its own stuff. I don't want to make a global callback for each instance I make, this doesnt seem clean and proper to me. What is the proper way of doing what I want. If I try to pass the threadproc to CreateThread and it is the proc from a class instance the compiler says I cannot do this. What is the best way of achieving what I want? Thanks

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  • C# How to kill parent thread

    - by Royson
    A parent has several child threads. If user click on stop button the parent thread should be killed with all child threads. //calls a main thread mainThread = new Thread(new ThreadStart(startWorking)); mainThread.Start(); //////////////////////////////////////////////// startWorking() { ManualResetEventInstance = new ManualResetEvent(false); ThreadPool.SetMaxThreads(m_ThreadPoolLimit, m_ThreadPoolLimit); for(int i = 0; i < list.count ; i++) { ThreadData obj_ThreadData = new ThreadData(); obj_ThreadData.name = list[i]; m_ThreadCount++; //execute WaitCallback obj_waitCallBack = new WaitCallback(startParsing); ThreadPool.QueueUserWorkItem(obj_waitCallBack, obj_ThreadData); } ManualResetEventInstance.WaitOne(); } I want to kill mainThread.

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  • Thread safe lazy contruction of a singleton in C++

    - by pauldoo
    Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before any code is executed (ie, even before static constructors are executed - their values may already be "initialized" in the program image)? If so - perhaps this can be exploited to implement a singleton mutex - which can in turn be used to guard the creation of the real singleton..) Excellent, it seems that I have a couple of good answers now (shame I can't mark 2 or 3 as being the answer). There appears to be two broad solutions: Use static initialisation (as opposed to dynamic initialisation) of a POD static varible, and implementing my own mutex with that using the builtin atomic instructions. This was the type of solution I was hinting at in my question, and I believe I knew already. Use some other library function like pthread_once or boost::call_once. These I certainly didn't know about - and am very grateful for the answers posted.

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  • Why is there no autorelease pool when I do performSelectorInBackground: ?

    - by Thanks
    I am calling a method that goes in a background thread: [self performSelectorInBackground:@selector(loadViewControllerWithIndex:) withObject:[NSNumber numberWithInt:viewControllerIndex]]; then, I have this method implementation that gets called by the selector: - (void) loadViewControllerWithIndex:(NSNumber *)indexNumberObj { NSAutoreleasePool *arPool = [[NSAutoreleasePool alloc] init]; NSInteger vcIndex = [indexNumberObj intValue]; Class c; UIViewController *controller = [viewControllers objectAtIndex:vcIndex]; switch (vcIndex) { case 0: c = [MyFirstViewController class]; break; case 1: c = [MySecondViewController class]; break; default: NSLog(@"unknown index for loading view controller: %d", vcIndex); // error break; } if ((NSNull *)controller == [NSNull null]) { controller = [[c alloc] initWithNib]; [viewControllers replaceObjectAtIndex:vcIndex withObject:controller]; [controller release]; } if (controller.view.superview == nil) { UIView *placeholderView = [viewControllerPlaceholderViews objectAtIndex:vcIndex]; [placeholderView addSubview:controller.view]; } [arPool release]; } Althoug I do create an autorelease pool there for that thread, I always get this error: 2009-05-30 12:03:09.910 Demo[1827:3f03] *** _NSAutoreleaseNoPool(): Object 0x523e50 of class NSCFNumber autoreleased with no pool in place - just leaking Stack: (0x95c83f0f 0x95b90442 0x28d3 0x2d42 0x95b96e0d 0x95b969b4 0x93a00155 0x93a00012) If I take away the autorelease pool, I get a whole bunch of messages like these. I also tried to create an autorelease pool around the call of the performSelectorInBackground:, but that doesn't help. I suspect the parameter, but I don't know why the compiler complains about an NSCFNumber. Am I missing something? My Instance variables are all "nonatomic". Can that be a problem? UPDATE: I may also suspect that some variable has been added to an autorelease pool of the main thread (maybe an ivar), and now it trys to release that one inside the wrong autorelease pool? If so, how could I fix that? (damn, this threading stuff is complex ;) )

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  • Thread pool in scala

    - by ghedas
    I have a project that is actor-based and for one part of it I must use some actors that receive message after that one actor assigns to each request separately and each actor is responsible for doing its message request, so I need something like a thread pool for actors of my project, are there any features in Scala that is useful for my necessity? how can I achieve this goal? tanks a lot for your attention!

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  • Pause and resume thread drawing to SurfaceView

    - by fhucho
    I am developing a chess game for Android (http://androidchess.appspot.com), using SurfaceView for the chessboard. I have a drawing Thread, that draws the chessboard in a loop. The problem is that when there are no active animations (this is more that 90% of time), it makes no sense to waste CPU and battery for drawing. How should I solve this? Maybe somehow pausing and resuming the drawing Thread?

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  • Would watching a file for changes or redundantly querying that file be more efficient?

    - by badpanda
    I am wondering whether watching a file/directory for changes using the FileSystemWatcher class is extremely memory intensive. I am developing a desktop application in C# that will be running behind the scenes continuously on low-performance computers, and I need some way of checking to see if various files have changed. I can think of a few solutions: Watch the directories using FileSystemWatcher. Run a timed thread on an interval that goes through and manually checks this. Check manually every time the actionhandler thread runs (the program will occasionally do something, on an action). Any suggestions? Thanks! badPanda

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  • How to correctly stop thread which is using Control.Invoke

    - by codymanix
    I tried the following (pseudocode) but I always get a deadlock when Iam trying to stop my thread. The problem is that Join() waits for the thread to complete and a pending Invoke() operation is also waiting to complete. How can I solve this? Thread workerThread = new Thread(BackupThreadRunner); volatile bool cancel; // this is the thread worker routine void BackupThreadRunner() { while (!cancel) { DoStuff(); ReportProgress(); } } // main thread void ReportProgress() { if (InvokeRequired) { Invoke(ReportProgress); } UpdateStatusBarAndStuff(); } // main thread void DoCancel() { cancel=true; workerThread.Join(); }

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  • Multiuser XML document "database" for asp.net app

    - by Pierreten
    I was thinking about a way to allow multiple users to get CRUD access to an XML document in an asp.net app. The operations would obviously have to be made under the assumption of a multithreaded environment. For perf reasons, would it make sense to cache the document, and use a mutex on that cached version? When would changes be flushed to the physical XML document? Any and all recommendations are appreciated (also "use a database" isn't an option at this point unfortunately)

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  • Threading cost - minimum execution time when threads would add speed

    - by Lukas
    I am working on a C# application that works with an array. It walks through it (meaning that at one time only a narrow part of the array is used). I am considering adding threads in it to make it perform faster (it runs on a dualcore computer). The problem is that I do not know if it would actually help, because threads cost something and this cost could easily be more than the parallel gain... So how do I determine if threading would help?

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  • Getting progress reports from a layered worker class?

    - by Slashdev
    I have a layered worker class that I'm trying to get progress reports from. What I have looks something like this: public class Form1 { private void Start_Click() { Controller controller = new Controller(); controller.RunProcess(); } } public class Controller { public void RunProcess() { Thread newThread = new Thread(new ThreadStart(DoEverything)); newThread.Start(); } private void DoEverything() { // Commencing operation... Class1 class1 = new Class1(); class1.DoStuff(); Class2 class2 = new Class2(); class2.DoMoreStuff(); } } public class Class1 { public void DoStuff() { // Doing stuff Thread.Sleep(1000); // Want to report progress here } } public class Class2 { public void DoMoreStuff() { // Doing more stuff Thread.Sleep(2000); // Want to report progress here as well } } I've used the BackgroundWorker class before, but I think I need something a bit more free form for something like this. I think I could use a delegate/event solution, but I'm not sure how to apply it here. Let's say I've got a few labels or something on Form1 that I want to be able to update with class1 and class2's progress, what's the best way to do that?

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  • Java assignment issues - Is this atomic?

    - by Bob
    Hi, I've got some questions about Java's assigment. Strings I've got a class: public class Test { private String s; public synchronized void setS(String str){ s = s + " - " + str; } public String getS(){ return s; } } I'm using "synchronized" in my setter, and avoiding it in my getter, because in my app, there are a tons of data gettings, and very few settings. Settings must be synchronized to avoid inconsistency. My question is: is getting and setting a variable atomic? I mean, in a multithreaded environment, Thread1 is about to set variable s, while Thread2 is about to get "s". Is there any way the getter method could get something different than the s's old value or the s's new value (suppose we've got only two threads)? In my app it is not a problem to get the new value, and it is not a problem to get the old one. But could I get something else? What about HashMap's getting and putting? considering this: public class Test { private Map<Integer, String> map = Collections.synchronizedMap(new HashMap<Integer, String>()); public synchronized void setMapElement(Integer key, String value){ map.put(key, value); } public String getValue(Integer key){ return map.get(key); } } Is putting and getting atomic? How does HashMap handle putting an element into it? Does it first remove the old value and put the now one? Could I get other than the old value or the new value? Thanks in advance!

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  • Unhandled exceptions in BackgroundWorker

    - by edg
    My WinForms app uses a number of BackgroundWorker objects to retrieve information from a database. I'm using BackgroundWorker because it allows the UI to remain unblocked during long-running database queries and it simplifies the threading model for me. I'm getting occasional DatabaseExceptions in some of these background threads, and I have witnessed at least one of these exceptions in a worker thread while debugging. I'm fairly confident these exceptions are timeouts which I suppose its reasonable to expect from time to time. My question is about what happens when an unhandled exception occurs in one of these background worker threads. I don't think I can catch an exception in another thread, but can I expect my WorkerCompleted method to be executed? Is there any property or method of the BackgroundWorker I can interrogate for exceptions?

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  • How to interrupt a thread performing a blocking socket connect?

    - by Jason R
    I have some code that spawns a pthread that attempts to maintain a socket connection to a remote host. If the connection is ever lost, it attempts to reconnect using a blocking connect() call on its socket. Since the code runs in a separate thread, I don't really care about the fact that it uses the synchronous socket API. That is, until it comes time for my application to exit. I would like to perform some semblance of an orderly shutdown, so I use thread synchronization primitives to wake up the thread and signal for it to exit, then perform a pthread_join() on the thread to wait for it to complete. This works great, unless the thread is in the middle of a connect() call when I command the shutdown. In that case, I have to wait for the connect to time out, which could be a long time. This makes the application appear to take a long time to shut down. What I would like to do is to interrupt the call to connect() in some way. After the call returns, the thread will notice my exit signal and shut down cleanly. Since connect() is a system call, I thought that I might be able to intentionally interrupt it using a signal (thus making the call return EINTR), but I'm not sure if this is a robust method in a POSIX threads environment. Does anyone have any recommendations on how to do this, either using signals or via some other method? As a note, the connect() call is down in some library code that I cannot modify, so changing to a non-blocking socket is not an option.

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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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  • Impossible to be const-correct when combining data and it's lock?

    - by Graeme
    I've been looking at ways to combine a piece of data which will be accessed by multiple threads alongside the lock provisioned for thread-safety. I think I've got to a point where I don't think its possible to do this whilst maintaining const-correctness. Take the following class for example: template <typename TType, typename TMutex> class basic_lockable_type { public: typedef TMutex lock_type; public: template <typename... TArgs> explicit basic_lockable_type(TArgs&&... args) : TType(std::forward<TArgs...>(args)...) {} TType& data() { return data_; } const TType& data() const { return data_; } void lock() { mutex_.lock(); } void unlock() { mutex_.unlock(); } private: TType data_; mutable TMutex mutex_; }; typedef basic_lockable_type<std::vector<int>, std::mutex> vector_with_lock; In this I try to combine the data and lock, marking mutex_ as mutable. Unfortunately this isn't enough as I see it because when used, vector_with_lock would have to be marked as mutable in order for a read operation to be performed from a const function which isn't entirely correct (data_ should be mutable from a const). void print_values() const { std::lock_guard<vector_with_lock>(values_); for(const int val : values_) { std::cout << val << std::endl; } } vector_with_lock values_; Can anyone see anyway around this such that const-correctness is maintained whilst combining data and lock? Also, have I made any incorrect assumptions here?

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