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  • Issue with Java join() method.

    - by gmunk
    First of all here are some code snippets: http://pastebin.com/9ZCwekXs http://pastebin.com/TtLLXPYP I'm trying to animate some images. The thing is that I want the main thread to wait for the animation thread to finish and then to continue. I searched around, read a little bit and decided to use the join() method. It perfectly waits for the thread to finish but I doesn't animate correctly. The repaint() method gets called 2 times instead of nine. I think maybe the problem is because I used singletons. Here is the singleton implementation. http://pastebin.com/bA3qLZJE

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  • Threading vs single thread

    - by user177883
    Is it always guaranteed that a multi-threaded application would run faster than a single threaded application? I have two threads that populates data from a data source but different entities (eg: database, from two different tables), seems like single threaded version of the application is running faster than the version with two threads. Why would the reason be? when i look at the performance monitor, both cpu s are very spikey ? is this due to context switching? what are the best practices to jack the CPU and fully utilize it? I hope this is not ambiguous.

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  • How to update GUI thread/class from worker thread/class?

    - by user315182
    First question here so hello everyone. The requirement I'm working on is a small test application that communicates with an external device over a serial port. The communication can take a long time, and the device can return all sorts of errors. The device is nicely abstracted in its own class that the GUI thread starts to run in its own thread and has the usual open/close/read data/write data basic functions. The GUI is also pretty simple - choose COM port, open, close, show data read or errors from device, allow modification and write back etc. The question is simply how to update the GUI from the device class? There are several distinct types of data the device deals with so I need a relatively generic bridge between the GUI form/thread class and the working device class/thread. In the GUI to device direction everything works fine with [Begin]Invoke calls for open/close/read/write etc. on various GUI generated events. I've read the thread here (How to update GUI from another thread in C#?) where the assumption is made that the GUI and worker thread are in the same class. Google searches throw up how to create a delegate or how to create the classic background worker but that's not at all what I need, although they may be part of the solution. So, is there a simple but generic structure that can be used? My level of C# is moderate and I've been programming all my working life, given a clue I'll figure it out (and post back)... Thanks in advance for any help.

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  • Asynchronous Delegates Vs Thread/ThreadPool?

    - by claws
    Hello, I need to execute 3 parallel tasks and after completion of each task they should call the same function which prints out the results. I don't understand in .net why we have Asychronous calling (delegate.BeginInvoke() & delegate.EndInvoke()) as well as Thread class? I'm little confused which one to use when? Now in this particular case, what should I use Asychronous calling or Thread class? I'm using C#.

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  • Multithreaded Unit Testing

    - by scope-creep
    Hi, Can anybody recommend any good books on unit testing for multitesting applications. Also can any body recommend appplications or utilities which can be used for multithreaded testing, similar to the java tool ConTest, (which i've not used but a fried recommended) Any help particularly related to C# unit testing for multithreaded apps in particularly welcome. thanks. Bob.

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  • Is Work Stealing always the most appropriate user-level thread scheduling algorithm?

    - by Il-Bhima
    I've been investigating different scheduling algorithms for a thread pool I am implementing. Due to the nature of the problem I am solving I can assume that the tasks being run in parallel are independent and do not spawn any new tasks. The tasks can be of varying sizes. I went immediately for the most popular scheduling algorithm "work stealing" using lock-free deques for the local job queues, and I am relatively happy with this approach. However I'm wondering whether there are any common cases where work-stealing is not the best approach. For this particular problem I have a good estimate of the size of each individual task. Work-stealing does not make use of this information and I'm wondering if there is any scheduler which will give better load-balancing than work-stealing with this information (obviously with the same efficiency). NB. This question ties up with a previous question.

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  • Does UIActivityIndicator require manual threading on iPhone

    - by Akusete
    I am running creating an iPhone application which performs a costly operation and I wanted to create an activityIndicator to let the user know the application has not frozen. The operation is performed entirely in one event call... so there is no chance for the UI framework to receive control to actually display and animate this indicator. The sample apps which use the UIActivityIndicator (or any other similar animation) start and stop the animation in different events, triggered separately at different stages of the program. Do I need to manually create a separate thread to run my operation in, or is there already default support for this kind of behavior?

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  • Thread.sleep vs Monitor.Wait vs RegisteredWaitHandle?

    - by Royi Namir
    (the following items has different goals , but im interesting knowing how they "PAUSEd") questions Thread.sleep - Does it impact performance on a system ?does it tie up a thread with its wait ? what about Monitor.Wait ? what is the difference in the way they "wait"? do they tie up a thread with their wait ? what aboutRegisteredWaitHandle ? This method accepts a delegate that is executed when a wait handle is signaled. While it’s waiting, it doesn’t tie up a thread. so some thread are paused and can be woken by a delegate , while others just wait ? spin ? can someone please make things clearer ? edit http://www.albahari.com/threading/part2.aspx

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  • Producer and Consumer Threads Hang

    - by user972425
    So this is my first foray into threads and thus far it is driving me insane. My problem seems to be some kind of synchronization error that causes my consumer thread to hang. I've looked at other code and just about everything I could find and I can't find what my error is. There also seems to be a discrepancy between the code being executed in Eclipse and via javac in the command line. Intention - Using a bounded buffer (with 1000 slots) create and consume 1,000,000 doubles. Use only notify and wait. Problem - In Eclipse the consumer thread will occasionally hang around 940,000 iterations, but other times completes. In the command line the consumer thread always hangs. Output - Eclipse - Successful Producer has produced 100000 doubles. Consumer has consumed 100000 doubles. Producer has produced 200000 doubles. Consumer has consumed 200000 doubles. Producer has produced 300000 doubles. Consumer has consumed 300000 doubles. Producer has produced 400000 doubles. Consumer has consumed 400000 doubles. Producer has produced 500000 doubles. Consumer has consumed 500000 doubles. Producer has produced 600000 doubles. Consumer has consumed 600000 doubles. Producer has produced 700000 doubles. Consumer has consumed 700000 doubles. Producer has produced 800000 doubles. Consumer has consumed 800000 doubles. Producer has produced 900000 doubles. Consumer has consumed 900000 doubles. Producer has produced 1000000 doubles. Producer has produced all items. Consumer has consumed 1000000 doubles. Consumer has consumed all items. Exitting Output - Command Line/Eclipse - Unsuccessful Producer has produced 100000 doubles. Consumer has consumed 100000 doubles. Producer has produced 200000 doubles. Consumer has consumed 200000 doubles. Producer has produced 300000 doubles. Consumer has consumed 300000 doubles. Producer has produced 400000 doubles. Consumer has consumed 400000 doubles. Producer has produced 500000 doubles. Consumer has consumed 500000 doubles. Producer has produced 600000 doubles. Consumer has consumed 600000 doubles. Producer has produced 700000 doubles. Consumer has consumed 700000 doubles. Producer has produced 800000 doubles. Consumer has consumed 800000 doubles. Producer has produced 900000 doubles. Consumer has consumed 900000 doubles. Producer has produced 1000000 doubles. Producer has produced all items. At this point it just sits and hangs. Any help you can provide about where I might have misstepped is greatly appreciated. Code - Producer thread import java.text.DecimalFormat;+ " doubles. Cumulative value of generated items= " + temp) import java.util.*; import java.io.*; public class producer implements Runnable{ private buffer produceBuff; public producer (buffer buff){ produceBuff = buff; } public void run(){ Random random = new Random(); double temp = 0, randomElem; DecimalFormat df = new DecimalFormat("#.###"); for(int i = 1; i<=1000000; i++) { randomElem = (Double.parseDouble( df.format(random.nextDouble() * 100.0))); try { produceBuff.add(randomElem); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } temp+= randomElem; if(i%100000 == 0) {produceBuff.print("Producer has produced "+ i ); } } produceBuff.print("Producer has produced all items."); } } Consumer thread import java.util.*; import java.io.*; public class consumer implements Runnable{ private buffer consumBuff; public consumer (buffer buff){ consumBuff = buff; } public void run(){ double temp = 0; for(int i = 1; i<=1000000; i++) { try { temp += consumBuff.get(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } if(i%100000 == 0) {consumBuff.print("Consumer has consumed "+ i ); //if(i>999000) //{System.out.println("Consuming item " + i);} } consumBuff.print("Consumer has consumed all items."); } } Buffer/Main import java.util.*; import java.io.*; public class buffer { private double buff[]; private int addPlace; private int getPlace; public buffer(){ buff = new double[1000]; addPlace = 0; getPlace = 0; } public synchronized void add(double add) throws InterruptedException{ if((addPlace+1 == getPlace) ) { try { wait(); } catch (InterruptedException e) {throw e;} } buff[addPlace] = add; addPlace = (addPlace+1)%1000; notify(); } public synchronized double get()throws InterruptedException{ if(getPlace == addPlace) { try { wait(); } catch (InterruptedException e) {throw e;} } double temp = buff[getPlace]; getPlace = (getPlace+1)%1000; notify(); return temp; } public synchronized void print(String view) { System.out.println(view); } public static void main(String args[]){ buffer buf = new buffer(); Thread produce = new Thread(new producer(buf)); Thread consume = new Thread(new consumer(buf)); produce.start(); consume.start(); try { produce.join(); consume.join(); } catch (InterruptedException e) {return;} System.out.println("Exitting"); } }

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  • Simple multi-threading - combining statements to two lines.

    - by Adam
    If I have: ThreadStart starter = delegate { MessageBox.Show("Test"); }; new Thread(starter).Start(); How can I combine this into one line of code? I've tried: new Thread(delegate { MessageBox.Show("Test"); }).Start(); But I get this error: The call is ambiguous between the following methods or properties: 'System.Threading.Thread.Thread(System.Threading.ThreadStart)' and 'System.Threading.Thread.Thread(System.Threading.ParameterizedThreadStart)'

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  • My Thread Programs Crash

    - by zp26
    I have a problem with threads objectiveC. The line of code below contains the recv block the program waiting for a datum. My intention is to launch a thread parallel to the program so that this statement does not block any application. I put this code in my program but when active switch the program crashes. Enter the code. -(IBAction)Chat{ if(switchChat.on){ buttonInvio.enabled = TRUE; fieldInvio.enabled = TRUE; [NSThread detachNewThreadSelector:@selector(riceviDatiServer) toTarget:self withObject:nil]; } else { buttonInvio.enabled = FALSE; fieldInvio.enabled = FALSE; } -(void)riceviDatiServer{ NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init]; int ricevuti; NSString *datiRicevuti; ricevuti = recv(temp, &datiRicevuti, datiRicevuti.length, 0); labelRicezione.text = [[NSString alloc] initWithFormat:@"%s.... %d", datiRicevuti, ricevuti]; [pool release]; }

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  • Is System.nanoTime() consistent across threads?

    - by obvio171
    I want to count the time elapsed between two events in nanoseconds. To do that, I can use System.nanoTime() as mentioned here. The problem is that the two events are happening in different threads. Since nanoTime() doesn't return an absolute timestamp but instead can only be used to calculate time differences, I'd like to know if the values I get on the two different threads are consistent with the physical time elapsed between the two events.

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  • Testing approach for multi-threaded software

    - by Shane MacLaughlin
    I have a piece of mature geospatial software that has recently had areas rewritten to take better advantage of the multiple processors available in modern PCs. Specifically, display, GUI, spatial searching, and main processing have all been hived off to seperate threads. The software has a pretty sizeable GUI automation suite for functional regression, and another smaller one for performance regression. While all automated tests are passing, I'm not convinced that they provide nearly enough coverage in terms of finding bugs relating race conditions, deadlocks, and other nasties associated with multi-threading. What techniques would you use to see if such bugs exist? What techniques would you advocate for rooting them out, assuming there are some in there to root out? What I'm doing so far is running the GUI functional automation on the app running under a debugger, such that I can break out of deadlocks and catch crashes, and plan to make a bounds checker build and repeat the tests against that version. I've also carried out a static analysis of the source via PC-Lint with the hope of locating potential dead locks, but not had any worthwhile results. The application is C++, MFC, mulitple document/view, with a number of threads per doc. The locking mechanism I'm using is based on an object that includes a pointer to a CMutex, which is locked in the ctor and freed in the dtor. I use local variables of this object to lock various bits of code as required, and my mutex has a time out that fires my a warning if the timeout is reached. I avoid locking where possible, using resource copies where possible instead. What other tests would you carry out?

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  • Different standard streams per POSIX thread

    - by Roman Nikitchenko
    Is there any possibility to achieve different redirections for standard output like printf(3) for different POSIX thread? What about standard input? I have lot of code based on standard input/output and I only can separate this code into different POSIX thread, not process. Linux operation system, C standard library. I know I can refactor code to replace printf() to fprintf() and further in this style. But in this case I need to provide some kind of context which old code doesn't have. So doesn't anybody have better idea (look into code below)? #include <pthread.h> #include <stdio.h> void* different_thread(void*) { // Something to redirect standard output which doesn't affect main thread. // ... // printf() shall go to different stream. printf("subthread test\n"); return NULL; } int main() { pthread_t id; pthread_create(&id, NULL, different_thread, NULL); // In main thread things should be printed normally... printf("main thread test\n"); pthread_join(id, NULL); return 0; }

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  • What is the JVM Scheduling algorithm ?

    - by IHawk
    Hello ! I am really curious about how does the JVM work with threads ! In my searches in internet, I found some material about RTSJ, but I don't know if it's the right directions for my answers. I also found this topic in sun's forums, http://forums.sun.com/thread.jspa?forumID=513&threadID=472453, but that's not satisfatory. Can someone give me some directions, material, articles or suggestion about the JVM scheduling algorithm ? I am also looking for information about the default configurations of Java threads in the scheduler, like 'how long does it take for every thread' in case of time-slicing. And this stuff. I would appreciate any help ! Thank you !

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  • Is ReaderWriterLockSlim.EnterUpgradeableReadLock() essentially the same as Monitor.Enter()?

    - by Neil Barnwell
    So I have a situation where I may have many, many reads and only the occasional write to a resource shared between multiple threads. A long time ago I read about ReaderWriterLock, and have read about ReaderWriterGate which attempts to mitigate the issue where many writes coming in trump reads and hurt performance. However, now I've become aware of ReaderWriterLockSlim... From the docs, I believe that there can only be one thread in "upgradeable mode" at any one time. In a situation where the only access I'm using is EnterUpgradeableReadLock() (which is appropriate for my scenario) then is there much difference to just sticking with lock(){}? Here's the excerpt: A thread that tries to enter upgradeable mode blocks if there is already a thread in upgradeable mode, if there are threads waiting to enter write mode, or if there is a single thread in write mode. Or, does the recursion policy make any difference to this?

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  • help me reason about F# threads

    - by Kevin Cantu
    In goofing around with some F# (via MonoDevelop), I have written a routine which lists files in a directory with one thread: let rec loop (path:string) = Array.append ( path |> Directory.GetFiles ) ( path |> Directory.GetDirectories |> Array.map loop |> Array.concat ) And then an asynchronous version of it: let rec loopPar (path:string) = Array.append ( path |> Directory.GetFiles ) ( let paths = path |> Directory.GetDirectories if paths <> [||] then [| for p in paths -> async { return (loopPar p) } |] |> Async.Parallel |> Async.RunSynchronously |> Array.concat else [||] ) On small directories, the asynchronous version works fine. On bigger directories (e.g. many thousands of directories and files), the asynchronous version seems to hang. What am I missing? I know that creating thousands of threads is never going to be the most efficient solution -- I only have 8 CPUs -- but I am baffled that for larger directories the asynchronous function just doesn't respond (even after a half hour). It doesn't visibly fail, though, which baffles me. Is there a thread pool which is exhausted? How do these threads actually work?

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  • ReaderWriterLockSlim and Pulse/Wait

    - by Jono
    Is there an equivalent of Monitor.Pulse and Monitor.Wait that I can use in conjunction with a ReaderWriterLockSlim? I have a class where I've encapsulated multi-threaded access to an underlying queue. To enqueue something, I acquire a lock that protects the underlying queue (and a couple of other objects) then add the item and Monitor.Pulse the locked object to signal that something was added to the queue. public void Enqueue(ITask task) { lock (mutex) { underlying.Enqueue(task); Monitor.Pulse(mutex); } } On the other end of the queue, I have a single background thread that continuously processes messages as they arrive on the queue. It uses Monitor.Wait when there are no items in the queue, to avoid unnecessary polling. (I consider this to be good design, but any flames (within reason) are welcome if they help me learn otherwise.) private void DequeueForProcessing(object state) { while (true) { ITask task; lock (mutex) { while (underlying.Count == 0) { Monitor.Wait(mutex); } task = underlying.Dequeue(); } Process(task); } } As more operations are added to this class (requiring read-only access to the lock protected underlying), someone suggested using ReaderWriterLockSlim. I've never used the class before, and assuming it can offer some performance benefit, I'm not against it, but only if I can keep the Pulse/Wait design.

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  • Thread locking issue with FileHelpers between calling engine.ReadNext() method and readign engine.Li

    - by Rad
    I use producer/consumer pattern with FileHelpers library to import data from one file (which can be huge) using multiple threads. Each thread is supposed to import a chunk of that file and I would like to use LineNumber property of the FileHelperAsyncEngine instance that is reading the file as primary key for imported rows. FileHelperAsyncEngine internally has an IEnumerator IEnumerable.GetEnumerator(); which is iterated over using engine.ReadNext() method. That internally sets LineNumber property (which seems is not thread safe). Consumers will have Producers assiciated with them that will supply DataTables to Consumers which will consume them via SqlBulkLoad class which will use IDataReader implementation which will iterate over a collection of DataTables which are internal to a Consumer instance. Each instance of will have one SqlBulkCopy instance associate with it. I have thread locking issue. Below is how I create multiple Producer threads. I start each thread afterwords. Produce method on a producer instance will be called determining which chunk of input file will be processed. It seems that engine.LineNumber is not thread safe and I doesn't import a proper LineNumber in the database. It seems that by the time engine.LineNumber is read some other thread called engine.ReadNext() and changed engine.LineNumber property. I don't want to lock the loop that is supposed to process a chunk of input file because I loose parallelism. How to reorganize the code to solve this threading issue? Thanks Rad for (int i = 0; i < numberOfProducerThreads; i++) DataConsumer consumer = dataConsumers[i]; //create a new producer DataProducer producer = new DataProducer(); //consumer has already being created consumer.Subscribe(producer); FileHelperAsyncEngine orderDetailEngine = new FileHelperAsyncEngine(recordType); orderDetailEngine.Options.RecordCondition.Condition = RecordCondition.ExcludeIfBegins; orderDetailEngine.Options.RecordCondition.Selector = STR_ORDR; int skipLines = i * numberOfBufferTablesToProcess * DataBuffer.MaxBufferRowCount; Thread newThread = new Thread(() => { producer.Produce(consumer, inputFilePath, lineNumberFieldName, dict, orderDetailEngine, skipLines, numberOfBufferTablesToProcess); consumer.SetEndOfData(producer); }); producerThreads.Add(newThread); thread.Start();} public void Produce(DataConsumer consumer, string inputFilePath, string lineNumberFieldName, Dictionary<string, object> dict, FileHelperAsyncEngine engine, int skipLines, int numberOfBufferTablesToProcess) { lock (this) { engine.Options.IgnoreFirstLines = skipLines; engine.BeginReadFile(inputFilePath); } int rowCount = 1; DataTable buffer = consumer.BufferDataTable; while (engine.ReadNext() != null) { lock (this) { dict[lineNumberFieldName] = engine.LineNumber; buffer.Rows.Add(ObjectFieldsDataRowMapper.MapObjectFieldsToDataRow(engine.LastRecord, dict, buffer)); if (rowCount % DataBuffer.MaxBufferRowCount == 0) { consumer.AddBufferDataTable(buffer); buffer = consumer.BufferDataTable; } if (rowCount % (numberOfBufferTablesToProcess * DataBuffer.MaxBufferRowCount) == 0) { break; } rowCount++; } } if (buffer.Rows.Count > 0) { consumer.AddBufferDataTable(buffer); } engine.Close(); }

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  • Log RuntimeException thrown from thread created by Spring via the @Async annotation

    - by Eugen
    I'm having some difficulty logging RuntimeException from a thread. My system is: Java 7 (b118), Spring 3.0.5. The threads are not created by hand, but via Spring's @Async annotation, which creates it's own executor behind the scenes, so I don't really have the option of overriding any methods of the thread, FutureTask or anything low level. So my question is if Spring has any support or if there are any best practices for handling (logging) these type of exceptions? Any suggestions are appreciated. Thanks.

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  • How can one manage to fully use the newly enhanced Parallelism features in .NET 4.0?

    - by Will Marcouiller
    I am pretty much interested into using the newly enhanced Parallelism features in .NET 4.0. I have also seen some possibilities of using it in F#, as much as in C#. Despite, I can only see what PLINQ has to offer with, for example, the following: var query = from c in Customers.AsParallel() where (c.Name.Contains("customerNameLike") select c; There must for sure be some other use of this parallelism thing. Have you any other examples of using it? Is this particularly turned toward PLINQ, or are there other usage as easy as PLINQ? Thanks! =)

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  • java methods and race condition in a jsp/servlets application.

    - by A.S al-shammari
    Hi. Suppose that I have a method called doSomething() and I want to use this method in a multithreaded application (each servlet inherits from HttpServlet).I'm wondering if it is possible that a race condition will occur in the following cases: doSomething() is not staic method and it writes values to a database. doSomething() is static method but it does not write values to a database. what I have noticed that many methods in my application may lead to a race condition or dirty read/write. for example , I have a Poll System , and for each voting operation, a certain method will change a single cell value for that poll as the following: [poll_id | poll_data ] [1 | {choice_1 : 10, choice_2 : 20}] will the JSP/Servlets app solve these issues by itself, or I have to solve all that by myself? Thanks..

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