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• Writing a synchronized thread-safety wrapper for NavigableMap

  - by polygenelubricants

  java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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• StructureMap Configuration Per Thread/Request for the Full Dependency Chain

  - by Phil Sandler

  I've been using Structuremap for a few months now, and it has worked great on some smaller (green field) projects. Most of the configurations I have had to set up involve a single implementation per interface. In the cases where I needed to choose a specific implementation at runtime, I created a factory class that used ObjectFactory.GetNamedInstance<(). In the smaller projects, there were few enough of these cases where I was comfortable with the references to ObjectFactory. My understanding is that you want to limit these references as much as possible, and ideally only reference the ObjectFactory once. I am working to refactor a larger codebase to use IOC/StructureMap, and am finding that I may need many of these factory classes with ObjectFactory references to get what I need. Essentially, I am creating a "root service" with the ObjectFactory, so that everything in the dependency chain is managed by the container. The root service is created by name (i.e. "BuildCar", "BuildTruck"), and the services needed deeper in the dependency chain could also be constructed using the same name--so the "IAttachWheels" service could vary based on whether a car or truck is being built. Since the class that depends on IAttachWheels is the same in both configurations, I don't think I can use ConstructedBy in the registry to choose the implementation. Also, to be clear, the IAttachWheels implementations need to be managed by the container as well, because the dependency chain runs fairly deep. I looked briefly at Profiles as an option, but read (here on StackOverflow) that changing profiles essentially changes implementations for all threads. Is there a feature that is similar to profiles that is thread/request specific? Is the factory class that references ObjectFactory approach the right way to go? Any thoughts would be appreciated.

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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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• How to multi-thread this?

  - by WilliamKF

  I wish to have two threads. The first thread1 occasionally calls the following pseudo function: void waitForThread2() { if (thread2 is not idle) { return; } notifyThread2IamReady(); while (thread2IsExclusive) { } } The second thread2 is forever in the following pseudo loop: for (;;) { Notify thread1 I am idle. while (!thread1IsReady()) { } Notify thread1 I am exclusive. Do some work while thread1 is blocked. Notify thread1 I am busy. Do some work in parallel with thread1. } What is the best way to write this such that both thread1 and thread2 are kept as busy as possible on a machine with multiple cores. I would like to avoid long delays between notification in one thread and detection by the other. I tried using pthread condition variables but found the delay between thread2 doing 'notify thread1 I am busy' and the loop in waitForThread2() on thear2IsExclusive() can be up to almost one second delay. I then tried using a volatile sig_atomic_t shared variable to control the same, but something is going wrong, so I must not be doing it correctly.

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• Stop functions in 5 minutes if they dont end running

  - by george mano

  I want to add a feature in my project. I have 2 functions running in a for-loop because I want to find the solution of the functions in random arrays. I also have an function that makes random arrays. In each loop the array that is made by the random_array fun are the input of the 2 functions. The 2 functions print solutions in the screen , they dont return an argument. int main(){ for (i=0;i<50 i++) { arr1=ramdom_array(); func1(arr1) func2(arr1) } } I need to stop the functions running if they have not ended in 5 minutes. I have thought that I have to put in the functions something like this : void func1(array<array<int,4>,4> initial) { while (5minutes_not_passed) { //do staff if(solution==true) break; } } But I dont know what to put in the 5minutes_not_passed. the declaration of the functions are like this: void func1(array<array<int,4>,4> initial) void func2(array<array<int,4>,4> initial) I have found that I can use the thread library but I dont think meshing up with threads in a good idea. I believe something like a timer is needed. Note that the functions sometimes might end before 5 minutes.

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• How to show and update popup in 1 thread

  - by user3713986

  I have 1 app. 2 Forms are MainFrm and PopupFrm, 1 thread to update some information to PopupFrm Now to update PopupFrm i use: In MainFrm.cs private PopupFrm mypop; MainFrm() { .... PopupFrm mypop= new PopupFrm(); mypop.Show(); } MyThread() { Process GetData();... mypop.Update(); ... } In PopupFrm.cs public void Update() { this.Invoke((MethodInvoker)delegate .... }); } Problem here that mypopup alway display when MainFrm display (Start application not when has data to update). So i change MainFrm.cs to : private PopupFrm mypop; private bool firstdisplay=false; MainFrm() { .... PopupFrm mypop= new PopupFrm(); //mypop.Show(); } MyThread() { Process GetData();... if(!firstdisplay) { mypop.Show(); firstdisplay=true; } mypop.Update(); ... } But it can not update Popup GUI. So how can i fix this issue ? Thanks all.

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• bluetooth BluetoothSocket.connect() thread. how to close this thread

  - by Hia

  I am trying to make an android app that makes connection with bluetooth device. It works fine but when I call BluetoothSocket.connect() and it is not able to connect to devise its blocking. The thread and does not throw any exception. So when I try to close application while connect() is running its not responding. How can I cancel it? Used BluetoothSocket.close() in ... but still its not working for me. protected void simpleComm(Integer port) { // The documents tell us to cancel the discovery process. try { Method m = mmDevice.getClass().getMethod("createRfcommSocket", new Class[] { int.class }); mmSocket = (BluetoothSocket) m.invoke(mmDevice, port); mmSocket.connect(); // <== blocks untill is not connected Log.d(TAG, " connection success==="); }catch(Exception e){ if (!abort) { connectionFailed(); // Close the socket try { mmSocket.close(); // Start the service over to restart listening mode BluetoothService.this.start(); } catch (IOException e2) { Log.e(TAG,"unable to close() socket during connection failure", e2); } } return; } } public void cancel() { try { abort = true; mmSocket.close(); } catch (IOException e) { Log.e(TAG, "close() of connect socket failed", e); } }

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• "Unable to initialize module" warning after update PHP on CentOS 5.4

  - by ohho

  After upgrading PHP from 5.1x to 5.2.10, there are a lot of warning when php -v: [root@localhost ~]# php -v PHP Warning: PHP Startup: fileinfo: Unable to initialize module Module compiled with module API=20050922, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: mcrypt: Unable to initialize module Module compiled with module API=20050922, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: memcache: Unable to initialize module Module compiled with module API=20050922, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: mhash: Unable to initialize module Module compiled with module API=20050922, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: mssql: Unable to initialize module Module compiled with module API=20050922, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: readline: Unable to initialize module Module compiled with module API=20050922, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: tidy: Unable to initialize module Module compiled with module API=20050922, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=0 These options need to match in Unknown on line 0 PHP 5.2.10 (cli) (built: Nov 13 2009 11:24:03) Copyright (c) 1997-2009 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2009 Zend Technologies How can I fix that? Thanks!

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• MySQL Cluster 7.2: Over 8x Higher Performance than Cluster 7.1

  - by Mat Keep

  0 0 1 893 5092 Homework 42 11 5974 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Summary The scalability enhancements delivered by extensions to multi-threaded data nodes enables MySQL Cluster 7.2 to deliver over 8x higher performance than the previous MySQL Cluster 7.1 release on a recent benchmark What’s New in MySQL Cluster 7.2 MySQL Cluster 7.2 was released as GA (Generally Available) in February 2012, delivering many enhancements to performance on complex queries, new NoSQL Key / Value API, cross-data center replication and ease-of-use. These enhancements are summarized in the Figure below, and detailed in the MySQL Cluster New Features whitepaper Figure 1: Next Generation Web Services, Cross Data Center Replication and Ease-of-Use Once of the key enhancements delivered in MySQL Cluster 7.2 is extensions made to the multi-threading processes of the data nodes. Multi-Threaded Data Node Extensions The MySQL Cluster 7.2 data node is now functionally divided into seven thread types: 1) Local Data Manager threads (ldm). Note – these are sometimes also called LQH threads. 2) Transaction Coordinator threads (tc) 3) Asynchronous Replication threads (rep) 4) Schema Management threads (main) 5) Network receiver threads (recv) 6) Network send threads (send) 7) IO threads Each of these thread types are discussed in more detail below. MySQL Cluster 7.2 increases the maximum number of LDM threads from 4 to 16. The LDM contains the actual data, which means that when using 16 threads the data is more heavily partitioned (this is automatic in MySQL Cluster). Each LDM thread maintains its own set of data partitions, index partitions and REDO log. The number of LDM partitions per data node is not dynamically configurable, but it is possible, however, to map more than one partition onto each LDM thread, providing flexibility in modifying the number of LDM threads. The TC domain stores the state of in-flight transactions. This means that every new transaction can easily be assigned to a new TC thread. Testing has shown that in most cases 1 TC thread per 2 LDM threads is sufficient, and in many cases even 1 TC thread per 4 LDM threads is also acceptable. Testing also demonstrated that in some instances where the workload needed to sustain very high update loads it is necessary to configure 3 to 4 TC threads per 4 LDM threads. In the previous MySQL Cluster 7.1 release, only one TC thread was available. This limit has been increased to 16 TC threads in MySQL Cluster 7.2. The TC domain also manages the Adaptive Query Localization functionality introduced in MySQL Cluster 7.2 that significantly enhanced complex query performance by pushing JOIN operations down to the data nodes. Asynchronous Replication was separated into its own thread with the release of MySQL Cluster 7.1, and has not been modified in the latest 7.2 release. To scale the number of TC threads, it was necessary to separate the Schema Management domain from the TC domain. The schema management thread has little load, so is implemented with a single thread. The Network receiver domain was bound to 1 thread in MySQL Cluster 7.1. With the increase of threads in MySQL Cluster 7.2 it is also necessary to increase the number of recv threads to 8. This enables each receive thread to service one or more sockets used to communicate with other nodes the Cluster. The Network send thread is a new thread type introduced in MySQL Cluster 7.2. Previously other threads handled the sending operations themselves, which can provide for lower latency. To achieve highest throughput however, it has been necessary to create dedicated send threads, of which 8 can be configured. It is still possible to configure MySQL Cluster 7.2 to a legacy mode that does not use any of the send threads – useful for those workloads that are most sensitive to latency. The IO Thread is the final thread type and there have been no changes to this domain in MySQL Cluster 7.2. Multiple IO threads were already available, which could be configured to either one thread per open file, or to a fixed number of IO threads that handle the IO traffic. Except when using compression on disk, the IO threads typically have a very light load. Benchmarking the Scalability Enhancements The scalability enhancements discussed above have made it possible to scale CPU usage of each data node to more than 5x of that possible in MySQL Cluster 7.1. In addition, a number of bottlenecks have been removed, making it possible to scale data node performance by even more than 5x. Figure 2: MySQL Cluster 7.2 Delivers 8.4x Higher Performance than 7.1 The flexAsynch benchmark was used to compare MySQL Cluster 7.2 performance to 7.1 across an 8-node Intel Xeon x5670-based cluster of dual socket commodity servers (6 cores each). As the results demonstrate, MySQL Cluster 7.2 delivers over 8x higher performance per data nodes than MySQL Cluster 7.1. More details of this and other benchmarks will be published in a new whitepaper – coming soon, so stay tuned! In a following blog post, I’ll provide recommendations on optimum thread configurations for different types of server processor. You can also learn more from the Best Practices Guide to Optimizing Performance of MySQL Cluster Conclusion MySQL Cluster has achieved a range of impressive benchmark results, and set in context with the previous 7.1 release, is able to deliver over 8x higher performance per node. As a result, the multi-threaded data node extensions not only serve to increase performance of MySQL Cluster, they also enable users to achieve significantly improved levels of utilization from current and future generations of massively multi-core, multi-thread processor designs.

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• No matter what, I can't get this stupid progress bar to update from a thread!

  - by Synthetix

  I have a Windows app written in C (using gcc/MinGW) that works pretty well except for a few UI problems. One, I simply cannot get the progress bar to update from a thread. In fact, I probably can't get ANY UI stuff to update. Basically, I have a spawned thread that does some processing, and from that thread I attempt to update the progress bar in the main thread. I tried this by using PostMessage() to the main hwnd, but no luck even though I can do other things like open message boxes. However, it's unclear whether the message box is getting called within the thread or on the main thread. Here's some code: //in header/globally accessible HWND wnd; //main application window HWND progress_bar; //progress bar typedef struct { //to pass to thread DWORD mainThreadId; HWND mainHwnd; char *filename; } THREADSTUFF; //callback function LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam){ switch(msg){ case WM_CREATE:{ //create progress bar progress_bar = CreateWindowEx( 0, PROGRESS_CLASS, (LPCTSTR)NULL, WS_CHILD | WS_VISIBLE, 79,164,455,15, hwnd, (HMENU)20, NULL, NULL); break; } case WM_COMMAND:{ if(LOWORD(wParam)==2){ //do some processing in a thread //struct of stuff I need to pass to thread THREADSTUFF *threadStuff; threadStuff = (THREADSTUFF*)malloc(sizeof(*threadStuff)); threadStuff->mainThreadId = GetCurrentThreadId(); threadStuff->mainHwnd = hwnd; threadStuff->filename = (void*)&filename; hThread1 = CreateThread(NULL,0,convertFile (LPVOID)threadStuff,0,NULL); }else if(LOWORD(wParam)==5){ //update progress bar MessageBox(hwnd,"I got a message!", "Message", MB_OK | MB_ICONINFORMATION); PostMessage(progress_bar,PBM_STEPIT,0,CLR_DEFAULT); } break; } } } This all seems to work okay. The problem is in the thread: DWORD WINAPI convertFile(LPVOID params){ //get passed params, this works perfectly fine THREADSTUFF *tData = (THREADSTUFF*)params; MessageBox(tData->mainHwnd,tData->filename,"File name",MB_OK | MB_ICONINFORMATION); //yep PostThreadMessage(tData->mainThreadId,WM_COMMAND,5,0); //only shows message PostMessage(tData->mainHwnd,WM_COMMAND,5,0); //only shows message } When I say, "only shows message," that means the MessageBox() function in the callback works, but not the PostMessage() to update the position of the progress bar. What am I missing?

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• Thread feeding other MultiThreading

  - by alaamh

  I see it's easy to open pipe between two process using fork, but how we can passing open pipe to threads. Assume we need to pass out of PROGRAM A to PROGRAM B "may by more than one thread", PROGRAM B send his output to PROGRAM C #include <stdio.h> #include <stdlib.h> #include <pthread.h> struct targ_s { char* reader; }; void *thread1(void *arg) { struct targ_s *targ = (struct targ_s*) arg; int status, fd[2]; pid_t pid; pipe(fd); pid = fork(); if (pid == 0) { int fd = fileno( targ->fd_reader ); dup2(STDIN_FILENO, fd); close(fd[0]); dup2(fd[1], STDOUT_FILENO); close(fd[1]); execvp ("PROGRAM B", NULL); exit(1); } else { close(fd[1]); dup2(fd[0], STDIN_FILENO); close(fd[0]); execl("PROGRAM C", NULL); wait(&status); return NULL; } } int main(void) { FILE *fpipe; char *command = "PROGRAM A"; char buffer[1024]; if (!(fpipe = (FILE*) popen(command, "r"))) { perror("Problems with pipe"); exit(1); } char* outfile = "out.dat"; FILE* f = fopen (outfile, "wb"); int fd = fileno( f ); struct targ_s targ; targ.fd_reader = outfile; pthread_t thid; if (pthread_create(&thid, NULL, thread1, &targ) != 0) { perror("pthread_create() error"); exit(1); } int len; while (read(fpipe, buffer, sizeof (buffer)) != 0) { len = strlen(buffer); write(fd, buffer, len); } pclose(fpipe); return (0); }

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• In C# ,how do I terminate a thread that has had its call stack corrupted?

  - by Emil D

  I have a thread in my application that is running code that can potentially cause call stack corruption ( my application is a testing tool for dlls ). Assuming that I have a method of detecting if the child thread is misbehaving, how would I terminate it? From what I read, calling Thread.Abort() on the misbehaving thread would be equivalent to raising an exception inside it.I fear that that not be a good idea, provided the call stack of the thread might be corrupted.Any suggestions?

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• In Java Concurrency In Practice by Brian Goetz, why is the Memoizer class not annotated with @ThreadSafe?

  - by dig_dug

  Java Concurrency In Practice by Brian Goetz provides an example of a efficient scalable cache for concurrent use. The final version of the example showing the implementation for class Memoizer (pg 108) shows such a cache. I am wondering why the class is not annotated with @ThreadSafe? The client, class Factorizer, of the cache is properly annotated with @ThreadSafe. The appendix states that if a class is not annotated with either @ThreadSafe or @Immutable that it should be assumed that it isn't thread safe. Memoizer seems thread-safe though. Here is the code for Memoizer: public class Memoizer<A, V> implements Computable<A, V> { private final ConcurrentMap<A, Future<V>> cache = new ConcurrentHashMap<A, Future<V>>(); private final Computable<A, V> c; public Memoizer(Computable<A, V> c) { this.c = c; } public V compute(final A arg) throws InterruptedException { while (true) { Future<V> f = cache.get(arg); if (f == null) { Callable<V> eval = new Callable<V>() { public V call() throws InterruptedException { return c.compute(arg); } }; FutureTask<V> ft = new FutureTask<V>(eval); f = cache.putIfAbsent(arg, ft); if (f == null) { f = ft; ft.run(); } } try { return f.get(); } catch (CancellationException e) { cache.remove(arg, f); } catch (ExecutionException e) { throw launderThrowable(e.getCause()); } } } }

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• Using ThreadPool.QueueUserWorkItem in ASP.NET in a high traffic scenario

  - by Michael Hart

  I've always been under the impression that using the ThreadPool for (let's say non-critical) short-lived background tasks was considered best practice, even in ASP.NET, but then I came across this article that seems to suggest otherwise - the argument being that you should leave the ThreadPool to deal with ASP.NET related requests. So here's how I've been doing small asynchronous tasks so far: ThreadPool.QueueUserWorkItem(s => PostLog(logEvent)) And the article is suggesting instead to create a thread explicitly, similar to: new Thread(() => PostLog(logEvent)){ IsBackground = true }.Start() The first method has the advantage of being managed and bounded, but there's the potential (if the article is correct) that the background tasks are then vying for threads with ASP.NET request-handlers. The second method frees up the ThreadPool, but at the cost of being unbounded and thus potentially using up too many resources. So my question is, is the advice in the article correct? If your site was getting so much traffic that your ThreadPool was getting full, then is it better to go out-of-band, or would a full ThreadPool imply that you're getting to the limit of your resources anyway, in which case you shouldn't be trying to start your own threads? Clarification: I'm just asking in the scope of small non-critical asynchronous tasks (eg, remote logging), not expensive work items that would require a separate process (in these cases I agree you'll need a more robust solution).

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• Java performance problem with LinkedBlockingQueue

  - by lofthouses

  Hello, this is my first post on stackoverflow...i hope someone can help me i have a big performance regression with Java 6 LinkedBlockingQueue. In the first thread i generate some objects which i push in to the queue In the second thread i pull these objects out. The performance regression occurs when the take() method of the LinkedBlockingQueue is called frequently. I monitored the whole program and the take() method claimed the most time overall. And the throughput goes from ~58Mb/s to 0.9Mb/s... the queue pop and take methods ar called with a static method from this class public class C_myMessageQueue { private static final LinkedBlockingQueue<C_myMessageObject> x_queue = new LinkedBlockingQueue<C_myMessageObject>( 50000 ); /** * @param message * @throws InterruptedException * @throws NullPointerException */ public static void addMyMessage( C_myMessageObject message ) throws InterruptedException, NullPointerException { x_queue.put( message ); } /** * @return Die erste message der MesseageQueue * @throws InterruptedException */ public static C_myMessageObject getMyMessage() throws InterruptedException { return x_queue.take(); } } how can i tune the take() method to accomplish at least 25Mb/s, or is there a other class i can use which will block when the "queue" is full or empty. kind regards Bart P.S.: sorry for my bad english, i'm from germany ;)

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• How can I load file into web app through certain periods?

  - by Elena

  Hi all! I have next task: I need to load the same file into my web app several times, for example - twice a day! Suppose in that file I have information, that changes, and I need to load this info into my app to change the statistics for example. How can I load file several times (twice an hour, or twice a day)? What should I use? Is any algorithm to do that? I am not allowed to use external libraries like Quartz Scheduler. So I need to do it with Thread and/or Timer. Can anybody give me some example or algorithm how to do it. Where can I create the entry point to my Thread, can I do it in managed bean or I need some sort of filter/listener/servlet. I works with jsf and richFaces. Maybe in this technologies there are some algorithms to solve my problem. Any ideas? Thanks very much for help!

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• Parallel version of loop not faster than serial version

  - by Il-Bhima

  I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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• how to close a java frame with threads

  - by user261002

  I have a java frame that I want to close it automatically after 3 or 4 seconds. I found out I must used threads. but I dont know how exactly to do it, this a dumy part of my code : package intro; import java.awt.*; import java.io.IOException; //import view.LangMenu; public class IntroClass extends Frame { private int _screenWidth = 0; private int _screenHeight = 0; private int _screenCenterx = 0; private int _screenCentery = 0; //private static final String SOUND_PATH="/sounds/introSound.midi"; public IntroClass() { Toolkit thisScreen = Toolkit.getDefaultToolkit(); Dimension thisScrrensize = thisScreen.getScreenSize(); _screenWidth = thisScrrensize.width; _screenHeight = thisScrrensize.height; _screenCenterx = _screenWidth / 2; _screenCentery = _screenHeight / 2; setBackground(Color.pink); Label lbl = new Label("Welcome To Dots Game. Samaneh Khaleghi", Label.CENTER); add(lbl); setUndecorated(true); setLocation((_screenCenterx*50)/100,_screenCentery-(_screenCentery*50)/100); setSize((_screenWidth * 50) / 100, (_screenHeight * 50) / 100); WaitClass r = new WaitClass(); r.start(); view.DotsBoardFrame d=new view.DotsBoardFrame(); main.Main.showScreen(d); } class WaitClass extends Thread { boolean running = true; public void run() { while (running) { try { Thread.sleep(50); } catch (InterruptedException ex) { ex.printStackTrace(); } } } } }

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• Callers block until getFoo() has a value ready?

  - by Sean Owen

  I have a Java Thread which exposes a property which other threads want to access: class MyThread extends Thread { private Foo foo; ... Foo getFoo() { return foo; } ... public void run() { ... foo = makeTheFoo(); ... } } The problem is that it takes some short time from the time this runs until foo is available. Callers may call getFoo() before this and get a null. I'd rather they simply block, wait, and get the value once initialization has occurred. (foo is never changed afterwards.) It will be a matter of milliseconds until it's ready, so I'm comfortable with this approach. Now, I can make this happen with wait() and notifyAll() and there's a 95% chance I'll do it right. But I'm wondering how you all would do it; is there a primitive in java.util.concurrent that would do this, that I've missed? Or, how would you structure it? Yes, make foo volatile. Yes, synchronize on an internal lock Object and put the check in a while loop until it's not null. Am I missing anything?

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• Crash using WscRegisterForChanges.

  - by user335126

  I'm trying to use the WscRegisterForChanges with C++ function in Windows 7. Documentation located here: http://msdn.microsoft.com/en-us/library/bb432507(v=VS.85).aspx My problem is that even though the callback properly executes, the code crashes when it gets to the end of the callback's execution. Here's the code in question. It's very simple, so I'm not sure why it's crashing: #include #include #include void SecurityCenterChangeOccurred(void *param) { printf("Change occurred!\n"); } int main() { HRESULT result = S_OK; HANDLE callbackRegistration = NULL; result = WscRegisterForChanges( NULL, &callbackRegistration, (LPTHREAD_START_ROUTINE)SecurityCenterChangeOccurred, NULL); while(1) { Sleep(100); } return 0; } My call stack looks like this when the crash occurs: 00faf6e8() ntdll.dll!_TppWorkerThread@4() + 0x1293 bytes kernel32.dll!@BaseThreadInitThunk@12() + 0x12 bytes ntdll.dll!___RtlUserThreadStart@8() + 0x27 bytes ntdll.dll!__RtlUserThreadStart@8() + 0x1b bytes If I add ExitThread(0); to the end of SecurityCenterChangeOccurred, I get an error and the following trace (So I don't think I should be using ExitThread): Unhandled exception at 0x7799852b (ntdll.dll) in WscRegisterForChangesCrash.exe: 0xC000071C: An invalid thread, handle %p, is specified for this operation. Possibly, a threadpool worker thread was specified. ntdll.dll!_TpCheckTerminateWorker@4() + 0x3ca2f bytes ntdll.dll!_RtlExitUserThread@4() + 0x30 bytes WscRegisterForChangesCrash.exe!SecurityCenterChangeOccurred(void * param=0x00000000) Line 8 + 0xa bytes C++ wscapi.dll!WorkItemWrapper() + 0x19 bytes ntdll.dll!_RtlpTpWorkCallback@8() + 0xdf bytes ntdll.dll!_TppWorkerThread@4() + 0x1293 bytes kernel32.dll!@BaseThreadInitThunk@12() + 0x12 bytes ntdll.dll!___RtlUserThreadStart@8() + 0x27 bytes ntdll.dll!__RtlUserThreadStart@8() + 0x1b bytes Does anyone have any ideas why this might be happening? To trigger the crash run the program and turn the firewall on or off.

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• How to implement a multi-threaded asynchronous operation?

  - by drowneath

  Here's how my current approach looks like: // Somewhere in a UI class // Called when a button called "Start" clicked MyWindow::OnStartClicked(Event &sender) { _thread = new boost::thread(boost::bind(&MyWindow::WorkToDo, this)); } MyWindow::WorkToDo() { for(int i = 1; i < 10000000; i++) { int percentage = (int)((float)i / 100000000.f); _progressBar->SetValue(percentage); _statusText->SetText("Working... %d%%", percentage); printf("Pretend to do something useful...\n"); } } // Called on every frame MyWindow::OnUpdate() { if(_thread != 0 && _thread->timed_join(boost::posix_time::seconds(0)) { _progressBar->SetValue(100); _statusText->SetText("Completed!"); delete _thread; _thread = 0; } } But I'm afraid this is far from safe since I keep getting unhandled exception at the end of the program execution. I basically want to separate a heavy task into another thread without blocking the GUI part.

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• Bulletin Board System with tagging, email notification

  - by user678220

  I am looking for nice BBS system, Bulletin Board System, Discussion Board, or nice in-company communication platform. There are lots of people, about 30 people, joining in our project. We would like to share idea among us on that platform. We can post questions and concerns related with the project, and we would like to respond each other. Here is my list of functionality I want: Tagging Thread e.g) Announcement, Finance, Legal, Idea. One thread can have multiple Tags. members can set on/off to receive email when new comments are posted. They can set on/off on each Tag. e.g) one member on to receive email related with "Announcement", but off to receive "Finance". Thread owner can change threads' tag any time. Thread can have several type of post. Thread can be "vote" thread. Everyone can vote their opinion. Thread can be "action plan" thread. In this thread, "who" will "what" remains in the thread. By viewing all "action plan" thread, all action plans needed in the company is visualized.

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• Context switches much slower in new linux kernels

  - by Michael Goldshteyn

  We are looking to upgrade the OS on our servers from Ubuntu 10.04 LTS to Ubuntu 12.04 LTS. Unfortunately, it seems that the latency to run a thread that has become runnable has significantly increased from the 2.6 kernel to the 3.2 kernel. In fact the latency numbers we are getting are hard to believe. Let me be more specific about the test. We have a program that has two threads. The first thread gets the current time (in ticks using RDTSC) and then signals a condition variable once a second. The second thread waits on the condition variable and wakes up when it is signaled. It then gets the current time (in ticks using RDTSC). The difference between the time in the second thread and the time in the first thread is computed and displayed on the console. After this the second thread waits on the condition variable once more. So, we get a thread to thread signaling latency measurement once a second as a result. In linux 2.6.32, this latency is somewhere on the order of 2.8-3.5 us, which is reasonable. In linux 3.2.0, this latency is somewhere on the order of 40-100 us. I have excluded any differences in hardware between the two host hosts. They run on identical hardware (dual socket X5687 {Westmere-EP} processors running at 3.6 GHz with hyperthreading, speedstep and all C states turned off). We are changing the affinity to run both threads on physical cores of the same socket (i.e., the first thread is run on Core 0 and the second thread is run on Core 1), so there is no bouncing of threads on cores or bouncing/communication between sockets. The only difference between the two hosts is that one is running Ubuntu 10.04 LTS with kernel 2.6.32-28 (the fast context switch box) and the other is running the latest Ubuntu 12.04 LTS with kernel 3.2.0-23 (the slow context switch box). Have there been any changes in the kernel that could account for this ridiculous slow down in how long it takes for a thread to be scheduled to run?

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• Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/xmlbeans/XmlException

  - by Dheeraj kumar

  Hi, I have to read xls file in java.I used poi-3.6 to read xls file in Eclipse.But i m getting this ERROR"Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/xmlbeans/XmlException at ReadExcel2.main(ReadExcel2.java:38)". I have added following jars 1)poi-3.6-20091214.jar 2)poi-contrib-3.6-20091214.jar 3)poi-examples-3.6-20091214.jar 4)poi-ooxml-3.6-20091214.jar 5)poi-ooxml-schemas-3.6-20091214.jar 6)poi-scratchpad-3.6-20091214.jar Below is the code which i m using: import org.apache.poi.ss.usermodel.Workbook; import org.apache.poi.ss.usermodel.Sheet; import org.apache.poi.ss.usermodel.Row; import org.apache.poi.ss.usermodel.Cell; import org.apache.poi.xssf.usermodel.XSSFWorkbook; import org.apache.poi.xssf.usermodel.XSSFCell; import org.apache.poi.xssf.usermodel.XSSFRow; import java.io.FileInputStream; import java.io.IOException; import java.util.Iterator; import java.util.List; import java.util.ArrayList; public class ReadExcel { public static void main(String[] args) throws Exception { // // An excel file name. You can create a file name with a full path // information. // String filename = "C:\\myExcel.xl"; // // Create an ArrayList to store the data read from excel sheet. // List sheetData = new ArrayList(); FileInputStream fis = null; try { // // Create a FileInputStream that will be use to read the excel file. // fis = new FileInputStream(filename); // // Create an excel workbook from the file system. // // HSSFWorkbook workbook = new HSSFWorkbook(fis); Workbook workbook = new XSSFWorkbook(fis); // // Get the first sheet on the workbook. // Sheet sheet = workbook.getSheetAt(0); // // When we have a sheet object in hand we can iterator on each // sheet's rows and on each row's cells. We store the data read // on an ArrayList so that we can printed the content of the excel // to the console. // Iterator rows = sheet.rowIterator(); while (rows.hasNext()) { Row row = (XSSFRow) rows.next(); Iterator cells = row.cellIterator(); List data = new ArrayList(); while (cells.hasNext()) { Cell cell = (XSSFCell) cells.next(); data.add(cell); } sheetData.add(data); } } catch (IOException e) { e.printStackTrace(); } finally { if (fis != null) { fis.close(); } } showExelData(sheetData); } private static void showExelData(List sheetData) { // // Iterates the data and print it out to the console. // for (int i = 0; i < sheetData.size(); i++) { List list = (List) sheetData.get(i); for (int j = 0; j < list.size(); j++) { Cell cell = (XSSFCell) list.get(j); System.out.print(cell.getRichStringCellValue().getString()); if (j < list.size() - 1) { System.out.print(", "); } } System.out.println(""); } } } Please help. thanks in anticipation, Regards, Dheeraj!

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• Exception in thread "main" java.lang.NoSuchMethodError: sun/misc/Unsafe.allocateDBBMemory

  - by user2524935

  Has anyone been able to compile JRuby on a s390x Linux system? I am trying to use LogStash, which apparently requires JRuby, however SLES 11 has no JRuby repo included. jar ant produces the following. compile-annotation-binder: [javac] Compiling 18 source files to /home/user7/jruby-1.7.4/build/classes/jruby [javac] warning: [options] bootstrap class path not set in conjunction with -source 1.6 [javac] Note: /home/user7/jruby-1.7.4/src/org/jruby/util/CodegenUtils.java uses unchecked or unsafe operations. [javac] Note: Recompile with -Xlint:unchecked for details. [javac] 1 warning compile-jruby: [javac] Compiling 1395 source files to /home/user7/jruby-1.7.4/build/classes/jruby [javac] Exception in thread "main" java.lang.NoSuchMethodError: sun/misc/Unsafe.allocateDBBMemory(J)J [javac] at java.nio.DirectByteBuffer.(DirectByteBuffer.java:127) [javac] at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:306) [javac] at sun.misc.Perf.createLong(Native Method) [javac] at sun.misc.PerfCounter.(PerfCounter.java:77) [javac] at sun.misc.PerfCounter.newPerfCounter(PerfCounter.java:83) [javac] at sun.misc.PerfCounter$CoreCounters.(PerfCounter.java:140) [javac] at java.lang.J9VMInternals.initializeImpl(Native Method) [javac] at java.lang.J9VMInternals.initialize(J9VMInternals.java:236) [javac] at sun.misc.PerfCounter.getZipFileOpenTime(PerfCounter.java:194) [javac] at java.util.zip.ZipFile.(ZipFile.java:230) [javac] at java.util.zip.ZipFile.(ZipFile.java:159) [javac] at java.util.jar.JarFile.(JarFile.java:167) [javac] at java.util.jar.JarFile.(JarFile.java:104) [javac] at sun.misc.URLClassPath$JarLoader.getJarFile(URLClassPath.java:958) [javac] at sun.misc.URLClassPath$JarLoader.access$700(URLClassPath.java:826) [javac] at sun.misc.URLClassPath$JarLoader$1.run(URLClassPath.java:909) [javac] at sun.misc.URLClassPath$JarLoader$1.run(URLClassPath.java:899) [javac] at java.security.AccessController.doPrivileged(AccessController.java:280) [javac] at sun.misc.URLClassPath$JarLoader.ensureOpen(URLClassPath.java:898) [javac] at sun.misc.URLClassPath$JarLoader.(URLClassPath.java:871) [javac] at sun.misc.URLClassPath$3.rtJarLoader(URLClassPath.java:596) [javac] at sun.misc.URLClassPath$3.run(URLClassPath.java:546) [javac] at sun.misc.URLClassPath$3.run(URLClassPath.java:536) [javac] at java.security.AccessController.doPrivileged(AccessController.java:280) [javac] at sun.misc.URLClassPath.getLoader(URLClassPath.java:535) [javac] at sun.misc.URLClassPath.getLoader(URLClassPath.java:498) [javac] at sun.misc.URLClassPath.getResource(URLClassPath.java:324) [javac] at java.net.URLClassLoader$ClassFinder.run(URLClassLoader.java:1157) [javac] at java.security.AccessController.doPrivileged(AccessController.java:314) [javac] at java.net.URLClassLoader.findClass(URLClassLoader.java:594) [javac] at java.lang.ClassLoader.loadClassHelper(ClassLoader.java:743) [javac] at java.lang.ClassLoader.loadClass(ClassLoader.java:711) [javac] at java.lang.ClassLoader.loadClassHelper(ClassLoader.java:735) [javac] at java.lang.ClassLoader.loadClass(ClassLoader.java:711) [javac] at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:325) [javac] at java.lang.ClassLoader.loadClass(ClassLoader.java:690) [javac] at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:494) BUILD FAILED /home/user7/jruby-1.7.4/build.xml:636: The following error occurred while executing this line: /home/user7/jruby-1.7.4/build.xml:289: Compile failed; see the compiler error output for details. Total time: 1 minute 37 seconds Line 636 of build.xml <target name="jar" depends="init" description="Create the jruby.jar file. Used during dev."> -> <antcall target="jar-jruby" inheritall="true"/> </target> Line 289 of build.xml <javac destdir="${jruby.classes.dir}" fork="true" debug="true" source="${javac.version}" target="${javac.version}" -> deprecation="true" encoding="UTF-8" includeantruntime="true" memorymaximumsize="${jruby.compile.memory}"> <classpath refid="jruby.execute.classpath"/> <src path="${src.dir}"/> <exclude name="org/jruby/runtime/Constants.java"/> java -version java version "1.7.0" Java(TM) SE Runtime Environment (build pxz6470sr4fp1-20130325_01(SR4 FP1)) IBM J9 VM (build 2.6, JRE 1.7.0 Linux s390x-64 Compressed References 20130306_140761 (JIT enabled, AOT enabled) J9VM - R26_Java726_SR4_FP1_20130306_1011_B140761 JIT - r11.b03_20130131_32403ifx1 GC - R26_Java726_SR4_FP1_20130306_1011_B140761_CMPRSS J9CL - 20130306_140761) JCL - 20130315_01 based on Oracle 7u13-b08 ant -version Apache Ant version 1.7.1

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