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  • C++ volatile required when spinning on boost::shared_ptr operator bool()?

    - by JaredC
    I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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  • pthread_exit return value

    - by Manty
    This is surprising for me. void * thread_func(void *arg) { pthread_exit(&ret); } int main(void) { pthread_t thr; int *exit_status; pthread_create(&thr, NULL, thread_func, NULL); sleep(2); pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); ret = 20; pthread_join(thr, (void **)&exit_status); printf("value of exit status - %d\n", *exit_status); return 0; } The output is value of exit status - 50 value of exit status - 20 I was expecting both the times the exit_status would be the actual exit value(50 in my case) of the thread. Instead it is just returning the value of the global variable which I used for pthread_exit. Is it not a bug?

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  • Do I need to using locking against integers in c++ threads

    - by Shane MacLaughlin
    The title says it all really. If I am accessing a single integer type (e.g. long, int, bool, etc...) in multiple threads, do I need to use a synchronisation mechanism such as a mutex to lock them. My understanding is that as atomic types, I don't need to lock access to a single thread, but I see a lot of code out there that does use locking. Profiling such code shows that there is a significant performance hit for using locks, so I'd rather not. So if the item I'm accessing corresponds to a bus width integer (e.g. 4 bytes on a 32 bit processor) do I need to lock access to it when it is being used across multiple threads? Put another way, if thread A is writing to integer variable X at the same time as thread B is reading from the same variable, is it possible that thread B could end up a few bytes of the previous value mixed in with a few bytes of the value being written? Is this architecture dependent, e.g. ok for 4 byte integers on 32 bit systems but unsafe on 8 byte integers on 64 bit systems? Edit: Just saw this related post which helps a fair bit.

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  • Java: multi-threaded maps: how do the implementations compare?

    - by user346629
    I'm looking for a good hash map implementation. Specifically, one that's good for creating a large number of maps, most of them small. So memory is an issue. It should be thread-safe (though losing the odd put might be an OK compromise in return for better performance), and fast for both get and put. And I'd also like the moon on a stick, please, with a side-order of justice. The options I know are: HashMap. Disastrously un-thread safe. ConcurrentHashMap. My first choice, but this has a hefty memory footprint - about 2k per instance. Collections.sychronizedMap(HashMap). That's working OK for me, but I'm sure there must be faster alternatives. Trove or Colt - I think neither of these are thread-safe, but perhaps the code could be adapted to be thread safe. Any others? Any advice on what beats what when? Any really good new hash map algorithms that Java could use an implementation of? Thanks in advance for your input!

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  • What is better and why to use List as thread safe: BlockingCollection or ReaderWriterLockSlim or lock?

    - by theateist
    I have System.Collections.Generic.List _myList and many threads can read from it or add items to it simultaneously. From what I've read I should using 'BlockingCollection' so this will work. I also read about ReaderWriterLockSlim' and 'lock', but I don't figure out how to use them instead ofBlockingCollection`, so my question is can I do the same with: ReaderWriterLockSlim lock instead of using 'BlockingCollection'. If YES, can you please provide simple example and what pros and cons of using BlockingCollection, ReaderWriterLockSlim, lock?

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  • UITableViewController executes delate functions before network request finishes

    - by user1543132
    I'm having trouble trying to populate a UITableView with the results of a network request. It seems that my code is alright as it works perfectly when my network is speedy, however, when it's not, the function - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath- still executes, which results in a bad access error. I presume that this is because the array that the aforesaid function attempts to utilize has not been populated. This brings me to my question: Is there anyway that I can have the UITableView delegate methods delayed to avoid this? - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"AlbumsCell"; //UITableViewCell *basicCell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath]; AlbumsCell *cell = (AlbumsCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (!cell) { **// Here is where the Thread 1: EXC_BAD_ACCESS (code=2 address=0x8)** cell = [[[AlbumsCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } Album *album = [_albums objectAtIndex:[indexPath row]]; [cell setAlbum:album]; return cell; }

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  • How can I get back into my main processing thread?

    - by daveomcd
    I have an app that I'm accessing a remote website with NSURLConnection to run some code and then save out some XML files. I am then accessing those XML Files and parsing through them for information. The process works fine except that my User Interface isn't getting updated properly. I want to keep the user updated through my UILabel. I'm trying to update the text by using setBottomBarToUpdating:. It works the first time when I set it to "Processing Please Wait..."; however, in the connectionDidFinishLoading: it doesn't update. I'm thinking my NSURLConnection is running on a separate thread and my attempt with the dispatch_get_main_queue to update on the main thread isn't working. How can I alter my code to resolve this? Thanks! [If I need to include more information/code just let me know!] myFile.m NSLog(@"Refreshing..."); dispatch_sync( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ [self getResponse:@"http://mylocation/path/to/file.aspx"]; }); [self setBottomBarToUpdating:@"Processing Please Wait..."]; queue = dispatch_queue_create("updateQueue", DISPATCH_QUEUE_CONCURRENT); connectionDidFinishLoading: if ([response rangeOfString:@"Complete"].location == NSNotFound]) { // failed } else { //success dispatch_async(dispatch_get_main_queue(),^ { [self setBottomBarToUpdating:@"Updating Contacts..."]; }); [self updateFromXMLFile:@"http://thislocation.com/path/to/file.xml"]; dispatch_async(dispatch_get_main_queue(),^ { [self setBottomBarToUpdating:@"Updating Emails..."]; }); [self updateFromXMLFile:@"http://thislocation.com/path/to/file2.xml"]; }

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  • Locking individual elements in a static collection?

    - by user638474
    I have a static collection of objects that will be frequently updated from multiple threads. Is it possible to lock individual objects in a collection instead of locking the entire collection so that only threads trying to access the same object in the collection would get blocked instead of every thread? If there is a better way to update objects in a collection from multiple threads, I'm all ears.

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  • passing variables when calling methon in new thread (iphone)

    - by Mouhamad Lamaa
    dear stacks i need to pass variables to the thread method when creating a new thread my code is the follwing //generating thread [NSThread detachNewThreadSelector:@selector(startThread) toTarget:self withObject:nil]; thread job - (void)startThread:(NSInteger *)var img:(UIImageView *) Img{ NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; [NSThread sleepForTimeInterval:var]; [self performSelectorOnMainThread:@selector(threadMethod) withObject:nil waitUntilDone:NO]; //i need to pass Img to threadMethod: [pool release]; } thread Method - (void)threadMethod:(UIImageView *) Img { //do some coding. } so how i can do this (pass parameter to both of methods

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  • C++ thread to seperate process

    - by silverbandit91
    Is there any way i can have a thread branch off into it's 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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  • BackgroundWorker acting bizarrely...

    - by vdh_ant
    Hi guys I'm working on some code that calls a service. This service call could fail and if it does I want the system to try again until it works or too much time has passed. I am wondering where I am going wrong as the following code doesn't seem to be working correctly... It randomly only does one to four loops... protected virtual void ProcessAsync(object data, int count) { var worker = new BackgroundWorker(); worker.DoWork += (sender, e) => { throw new InvalidOperationException("oh shiznit!"); }; worker.RunWorkerCompleted += (sender, e) => { //If an error occurs we need to tell the data about it if (e.Error != null) { count++; System.Threading.Thread.Sleep(count * 5000); if (count <= 10) { if (count % 5 == 0) this.Logger.Fatal("LOAD ERROR - The system can't load any data", e.Error); else this.Logger.Error("LOAD ERROR - The system can't load any data", e.Error); this.ProcessAsync(data, count); } } }; worker.RunWorkerAsync(); } Cheers Anthony

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  • Thread-Safe lazy instantiating using MEF

    - by Xaqron
    // Member Variable private static readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { // It seems the `IsValueCreated` is not up-to-date if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile static int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. I should notice the CompositionContainer has a thread-safe option in constructor which is already used. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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  • C# Multi threading- Move objects between threads

    - by Grant
    Hi, i am working with a winforms control that is both a GUI element and also does some internal processing that has not been exposed to the developer. When this component is instantiated it may take between 5 and 15 seconds to become ready so what i want to do is put it on another thread and when its done bring it back to the gui thread and place it on my form. The problem is that this will (and has) cause a cross thread exception. Normally when i work with worker threads its just with simple data objects i can push back when processing is complete and then use with controls already on the main thread but ive never needed to move an entire control in this fashion. Does anyone know if this is possible and if so how? If not how does one deal with a problem like this where there is the potential to lock the main gui?

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  • Works on debug but not release

    - by user146780
    I have a thread that sets a value to true when it is done. Until then I wait: while(1) { if(done[0] == true) { break; } } This code works just fine in Debug but in Release it stays in the loop forever even though the debugger clearly says that it is true and not false. Why would this not work? Thanks

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  • Android thread handler NullPointerException

    - by Realn0whereman
    So this null pointer is confusing me. I believe it is a scope issue. My main activity looks like this: public class App extends Activity { ProgressDialog progressDialog; ProgressThread progressThread; Then inside of the oncreate I do this: ProgressDialog progressDialog = new ProgressDialog(this); progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER); progressDialog.setMessage("Fetching Images..."); ProgressThread progressThread = new ProgressThread(handler,mImageIds,mImages); progressThread.start(); progressDialog.show(); THEN inside progressThread which is a separate class I do mHandler.sendMessage(mHandler.obtainMessage()); Now up until this point i believe it behaves as it should. I have my handler hanging out in class scope right underneath my oncreate final Handler handler = new Handler() { public void handleMessage(Message msg){ progressDialog.hide(); progressThread.interrupt(); } }; The program thinks that progressDialog and progressThread are declared, but are null. Why would they be null if I instantiate in my oncreate.

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  • Interrupt a thread in DatagramSocket.receive

    - by SEK
    I'm building an application that listens on both TCP and UDP, and I've run into some trouble with my shutdown mechanism. When I call Thread.interrupt() on each of the listening threads, the TCP thread is interrupted from listening, whereas the UDP listener isn't. To be specific, the TCP thread uses Socket.accept(), which simply returns (without actually connecting). Whereas the UDP thread uses DatagramSocket.receive, and doesn't exit that method. Is this an issue in my JRE, my OS, or should I just switch to (Datagram)Socket.close()?

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  • lock statement not working when there is a loop inside it?

    - by Ngu Soon Hui
    See this code: public class multiply { public Thread myThread; public int Counter { get; private set; } public string name { get; private set; } public void RunConsolePrint() { lock(this) { RunLockCode("lock"); } } private void RunLockCode(string lockCode) { Console.WriteLine("Now thread "+lockCode+" " + name + " has started"); for (int i = 1; i <= Counter; i++) { Console.WriteLine(lockCode+" "+name + ": count has reached " + i + ": total count is " + Counter); } Console.WriteLine("Thread " + lockCode + " " + name + " has finished"); } public multiply(string pname, int pCounter) { name = pname; Counter = pCounter; myThread = new Thread(new ThreadStart(RunConsolePrint)); } } And this is the test run code: static void Main(string[] args) { int counter = 50; multiply m2 = new multiply("Second", counter); multiply m1 = new multiply("First", counter); m1.myThread.Start(); m2.myThread.Start(); Console.ReadLine(); } I would expect that m2 must execute from start to finish before m1 starts executing, or vice versa, because of the lock statement. But the result I found was the call to lock first and lock second was intermingled together, i.e., something like this Now thread lock First has started Now thread lock Second has started lock First: Count has reached 1: total count is 50 lock First: Count has reached 2: total count is 50 lock Second: Count has reached 1: total count is 50 What did I do wrong?

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  • C# Threading in a method

    - by user177883
    I have the following method : public List<string> someMethod() { // populate list of strings // dump them to csv file //return to output } Question is: i dont want the user to wait for csv dump, which might take a while. If i use a thread for csvdump, will it complete? before or after the return of output?

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  • Threading in java vs C#

    - by ffayyaz
    I need a little confirmation over something i am confused at . I know how threads work in java. new DialList(string a , string b).start(); // where DialList is a class public class DialList extends Thread { public DialList(String a, string b) { FilePath = a; ThreadLogFile = b"; } public void run() { // some code to run in different thread } } Now i want to run same code in C# , Shall i put the code which is in run() into a method and do something like Thread t = new Thread (runcsharp); // Kick off a new thread t.Start(); static void runcsharp() { // code } or is there some other way to do it ?

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  • Registering an event from different thread

    - by ET
    Hi, I have a question regarding events in c#. Lets say I have an object obj1 of a class that exposes an event, and this object is running on thread t1. Now on different thread t2, there is another object called obj2 that is registered for the event of obj1. Is it promised that obj2 will get the event when it will be raised? thanks.

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  • How to identify deadlock conditions in a third-party application?

    - by Imhotep is Invisible
    I am using a third-party application to handle batch CD audio extraction via multiple FireWire attached devices, but the application frequently (though non-deterministically) hangs during the extraction. I suspect that the multithreaded application is deadlocking over some shared resource. The developer, however, suspects the problem lies elsewhere but is not addressing the problem at this time. I would like to be able to do some legwork on my end to a) prove the condition exists and b) ideally point him in the right direction. The problems: while I used to be a programmer, it's been awhile and I need to shake off the dust (last work I did was back in '99 and it was under Solaris, while the application runs under XP). Rather than there being a dearth of information online, there's almost too much to digest. Are there any suggested guides or tutorials that might help me get back up to speed sufficient enough to help identify and/or diagnose the deadlock, or are there tools or approaches that I should study up on to aid me in my task? Many thanks for all suggestions!

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