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  • C# Alternating threads

    - by Mutoh
    Imagine a situation in which there are one king and n number of minions submissed to him. When the king says "One!", one of the minions says "Two!", but only one of them. That is, only the fastest minion speaks while the others must wait for another call of the king. This is my try: using System; using System.Threading; class Program { static bool leaderGO = false; void Leader() { do { lock(this) { //Console.WriteLine("? {0}", leaderGO); if (leaderGO) Monitor.Wait(this); Console.WriteLine("> One!"); Thread.Sleep(200); leaderGO = true; Monitor.Pulse(this); } } while(true); } void Follower (char chant) { do { lock(this) { //Console.WriteLine("! {0}", leaderGO); if (!leaderGO) Monitor.Wait(this); Console.WriteLine("{0} Two!", chant); leaderGO = false; Monitor.Pulse(this); } } while(true); } static void Main() { Console.WriteLine("Go!\n"); Program m = new Program(); Thread king = new Thread(() => m.Leader()); Thread minion1 = new Thread(() => m.Follower('#')); Thread minion2 = new Thread(() => m.Follower('$')); king.Start(); minion1.Start(); minion2.Start(); Console.ReadKey(); king.Abort(); minion1.Abort(); minion2.Abort(); } } The expected output would be this (# and $ representing the two different minions): > One! # Two! > One! $ Two! > One! $ Two! ... The order in which they'd appear doesn't matter, it'd be random. The problem, however, is that this code, when compiled, produces this instead: > One! # Two! $ Two! > One! # Two! > One! $ Two! # Two! ... That is, more than one minion speaks at the same time. This would cause quite the tumult with even more minions, and a king shoudln't allow a meddling of this kind. What would be a possible solution?

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  • What is the absolute fastest way to implement a concurrent queue with ONLY one consumer and one producer?

    - by JohnPristine
    java.util.concurrent.ConcurrentLinkedQueue comes to mind, but is it really optimum for this two-thread scenario? I am looking for the minimum latency possible on both sides (producer and consumer). If the queue is empty you can immediately return null AND if the queue is full you can immediately discard the entry you are offering. Does ConcurrentLinkedQueue use super fast and light locks (AtomicBoolean) ? Has anyone benchmarked ConcurrentLinkedQueue or knows about the ultimate fastest way of doing that? Additional Details: I imagine the queue should be a fair one, meaning the consumer should not make the consumer wait any longer than it needs (by front-running it) and vice-versa.

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  • "pseudo-atomic" operations in C++

    - by dan
    So I'm aware that nothing is atomic in C++. But I'm trying to figure out if there are any "pseudo-atomic" assumptions I can make. The reason is that I want to avoid using mutexes in some simple situations where I only need very weak guarantees. 1) Suppose I have globally defined volatile bool b, which initially I set true. Then I launch a thread which executes a loop while(b) doSomething(); Meanwhile, in another thread, I execute b=true. Can I assume that the first thread will continue to execute? In other words, if b starts out as true, and the first thread checks the value of b at the same time as the second thread assigns b=true, can I assume that the first thread will read the value of b as true? Or is it possible that at some intermediate point of the assignment b=true, the value of b might be read as false? 2) Now suppose that b is initially false. Then the first thread executes bool b1=b; bool b2=b; if(b1 && !b2) bad(); while the second thread executes b=true. Can I assume that bad() never gets called? 3) What about an int or other builtin types: suppose I have volatile int i, which is initially (say) 7, and then I assign i=7. Can I assume that, at any time during this operation, from any thread, the value of i will be equal to 7? 4) I have volatile int i=7, and then I execute i++ from some thread, and all other threads only read the value of i. Can I assume that i never has any value, in any thread, except for either 7 or 8? 5) I have volatile int i, from one thread I execute i=7, and from another I execute i=8. Afterwards, is i guaranteed to be either 7 or 8 (or whatever two values I have chosen to assign)?

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  • boost scoped_lock mutex crashes

    - by JahSumbar
    hello, I have protected a std::queue's access functions, push, pop, size, with boost::mutexes and boost::mutex::scoped_lock in these functions from time to time it crashes in a scoped lock the call stack is this: 0 0x0040f005 boost::detail::win32::interlocked_bit_test_and_set include/boost/thread/win32/thread_primitives.hpp 361 1 0x0040e879 boost::detail::basic_timed_mutex::timed_lock include/boost/thread/win32/basic_timed_mutex.hpp 68 2 0x0040e9d3 boost::detail::basic_timed_mutex::lock include/boost/thread/win32/basic_timed_mutex.hpp 64 3 0x0040b96b boost::unique_lock<boost::mutex>::lock include/boost/thread/locks.hpp 349 4 0x0040b998 unique_lock include/boost/thread/locks.hpp 227 5 0x00403837 MyClass::inboxSize - this is my inboxSize function that uses this code: MyClass::inboxSize () { boost::mutex::scoped_lock scoped_lock(m_inboxMutex); return m_inbox.size(); } and the mutex is declared like this: boost::mutex m_inboxMutex; it crashes at the last pasted line in this function: inline bool interlocked_bit_test_and_set(long* x,long bit) { long const value=1<<bit; long old=*x; and x has this value: 0xababac17 Thanks for the help

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  • Please tell me what is wrong with my threading!!!

    - by kiddo
    I have a function where I will compress a bunch of files into a single compressed file..it is taking a long time(to compress),so I tried implementing threading in my application..Say if I have 20 files for compression,I separated that as 5*4=20,inorder to do that I have separate variables(which are used for compression) for all 4 threads in order to avoid locks and I will wait until the 4 thread finishes..Now..the threads are working but i see no improvement in their performance..normally it will take 1 min for 20 files(for example) after implementing threading ...there is only 5 or 3 sec difference., sometimes the same. here i will show the code for 1 thread(so it is for other3 threads) //main thread myClassObject->thread1 = AfxBeginThread((AFX_THREADPROC)MyThreadFunction1,myClassObject); .... HANDLE threadHandles[4]; threadHandles[0] = myClassObject->thread1->m_hThread; .... WaitForSingleObject(myClassObject->thread1->m_hThread,INFINITE); UINT MyThreadFunction(LPARAM lparam) { CMerger* myClassObject = (CMerger*)lparam; CString outputPath = myClassObject->compressedFilePath.GetAt(0);//contains the o/p path wchar_t* compressInputData[] = {myClassObject->thread1outPath, COMPRESS,(wchar_t*)(LPCTSTR)(outputPath)}; HINSTANCE loadmyDll; loadmydll = LoadLibrary(myClassObject->thread1outPath); fp_Decompress callCompressAction = NULL; int getCompressResult=0; myClassObject->MyCompressFunction(compressInputData,loadClient7zdll,callCompressAction,myClassObject->thread1outPath, getCompressResult,minIndex,myClassObject->firstThread,myClassObject); return 0; }

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  • How can one use multi threading in php applications

    - by Steve Obbayi
    Is there a realistic way of implementing a multi-threaded model in php whether truly or just simulating it. Some time back it was suggested that you can force the operating system to load another instance of the php executable and handle other simultaneous processes. The problem with this is that when the php code finished executing the php instance remains in memory because there is no way to kill it from within php. so if you are simulating several threads you can imagine whats going to happen. So am still looking for a way multi-threading can be done or simulated effectively from within php. Any ideas?

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  • Reducing lag when downloading large amount of data from webpage

    - by Mahir
    I am getting data via RSS feeds and displaying each article in a table view cell. Each cell has an image view, set to a default image. If the page has an image, the image is to be replaced with the image from the article. As of now, each cell downloads the source code from the web page, causing the app to lag when I push the view controller and when I try scrolling. Here is what I have in the cellForRowAtIndexPath: method. NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; cell.picture.image = image; Someone suggested using NSOperationQueue. Would this way be a good solution? EDIT: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *MyIdentifier = @"FeedCell"; LMU_LAL_FeedCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier]; if (cell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"LMU_LAL_FeedCell" owner:self options:nil]; cell = (LMU_LAL_FeedCell*) [nib objectAtIndex:0]; } int storyIndex = [indexPath indexAtPosition: [indexPath length] - 1]; NSString *untrimmedTitle = [[stories objectAtIndex: storyIndex] objectForKey: @"title"]; cell.title.text = [untrimmedTitle stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; CGSize maximumLabelSize = CGSizeMake(205,9999); CGSize expectedLabelSize = [cell.title.text sizeWithFont:cell.title.font constrainedToSize:maximumLabelSize]; //adjust the label to the the new height. CGRect newFrame = cell.title.frame; newFrame.size.height = expectedLabelSize.height; cell.title.frame = newFrame; //position frame of date label CGRect dateNewFrame = cell.date.frame; dateNewFrame.origin.y = cell.title.frame.origin.y + cell.title.frame.size.height + 1; cell.date.frame = dateNewFrame; cell.date.text = [self formatDateAtIndex:storyIndex]; dispatch_queue_t someQueue = dispatch_queue_create("cell background queue", NULL); dispatch_async(someQueue, ^(void){ NSError *error = nil; NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; dispatch_async(dispatch_get_main_queue(), ^(void){ cell.picture.image = image; }); }) //error: expected expression } return cell; //error: expected identifier } //error extraneous closing brace

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  • Why onCreate() calling multiple times when i use Thread()?

    - by RajaReddy PolamReddy
    In my app i faced a problem with threads. i am using native code in my app. i try to load library and then calling native functions from the android code. 1. By using Threads() : PjsuaThread pjsuaThread = new PjsuaThread(); pjsuaThread.start(); thread code class PjsuaThread extends Thread { public void run() { if (pjsua_app.initApp() != 0) { // native function calling return; } else { } pjsua_app.startPjsua(ApjsuaActivity.CFG_FNAME); // native function calling finished = true; } When i use code like this, onCreate() function calling multiple times and able to load library and calling some functions properly, after some seconds onCreate calling again because of that it's crashing. 2. Using AsyncTask(): And also i used AsyncTask< for this requirement, it's crashing the application( crashing in lib code ). not able to open any functions class SipTask extends AsyncTask<Void, String, Void> { protected Void doInBackground(Void... args) { if (pjsua_app.initApp() != 0) { return null; } else { } pjsua_app.startPjsua(ApjsuaActivity.CFG_FNAME); finished = true; return null; } @Override protected void onPostExecute(Void result) { super.onPostExecute(result); Log.i(TAG, "On POst "); } } What is annoying is that in most cases it is not the missing library, it's tried to able to load the lib crashing in between. any one know the reason ?

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  • Thread Code...anything wrong with this, must use java 1.4

    - by bmw0128
    I have a servlet automatically firing up when the app server starts, and in its init(), I'm making another thread: init(){ new FooThread() } in FooThread(), i want to periodically check the status of a DB value, then depending on the value, make a web service call. When these two tasks complete, I want the thread to sleep to wait a certain period then repeat. This cycle would just continue forever. FooThread: public class FooThread implements Runnable{ Thread t; FooThread(){ t = new Thread(this, "BBSThread"); logger.info("*** about to start " + t.getName()); t.start(); logger.info("*** started: " + t); } public void run() { try{ while(true){ //do the db check, then conditionally do the web services call logger.info("*** calling sleep() ***"); Thread.sleep(50000); logger.info("*** now awake ***"); } } catch (InterruptedException e) { System.out.println("*** FooThread interrupted"); } } }

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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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  • Parent Thread exiting before Child Threads [python]

    - by crgwbr
    I'm using Python in a webapp (CGI for testing, FastCGI for production) that needs to send an occasional email (when a user registers or something else important happens). Since communicating with an SMTP server takes a long time, I'd like to spawn a thread for the mail function so that the rest of the app can finish up the request without waiting for the email to finish sending. I tried using thread.start_new(func, (args)), but the Parent return's and exits before the sending is complete, thereby killing the sending process before it does anything useful. Is there anyway to keep the process alive long enough for the child process to finish?

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  • Forcing an app to run single core only?

    - by Kevin
    I have this strange issue with some third party DLL's. The third party provider references some open source DLL's that have a memory exception whenever I try to use a certain method. This issue does not appear when the app is run on a single core machine, but obviously we cannot assume a user will have that. Is there a way to force an app, or even better yet a referenced DLL to run on a single core? Any other way to possibly fix this? Getting the third party to rebuild the OS dll's is apparently out of the question (its a bit of a sore spot with me currently :) ) so I have to handle it myself or just forget about providing this functionality.

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  • Look up values in a BDB for several files in parallel

    - by biznez
    What is the most efficient way to look up values in a BDB for several files in parallel? If I had a Perl script which did this for one file at a time, would forking/running the process in background with the ampersand in Linux work? How might Hadoop be used to solve this problem? Would threading be another solution?

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  • Java: "implements Runnable" vs. "extends Thread"

    - by goosefraba19
    From what time I've spent with threads in Java, I've found these two ways to write threads. public class ThreadA implements Runnable { public void run() { //Code } } //with a "new Thread(threadA).start()" call public class ThreadB extends Thread { public ThreadB() { super("ThreadB"); } public void run() { //Code } } //with a "threadB.start()" call Is there any significant difference in these two blocks of code?

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  • Failing faster when URL content is not found, howto

    - by Jam
    I have a thread pool that loops over a bunch of pages and checks to see if some string is there or not. If String is found, or not found response is near instant, however if server is offline or application is not running getting a rejection seems to take seconds How can I change my code to fail faster? for (Thread thread : pool) { thread.start(); } for (Thread thread : pool) { try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } } Here is my run method @Override public void run() { for (Box b : boxes) { try { connection = new URL(b.getUrl()).openConnection(); scanner = new Scanner(connection.getInputStream()); scanner.useDelimiter("\\Z"); content = scanner.next(); if (content.equals("YES")) { } else { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } catch (Exception ex) { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } }

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  • Thread is being killed by the OS

    - by Or.Ron
    I'm currently programming an app that extracts frames from a movie clip. I designed it so that the extraction will be done on a separate thread to prevent the application from freezing. The extraction process itself is taking a lot of resources, but works fine when used in the simulator. However, there are problems when building it for the iPad. When I perform another action (I'm telling my AV player to play while I extract frames), the thread unexpectedly stops working, and I believe it's being killed. I assume it's becauase I'm using a lot of resources, but not entirely sure. Here are my questions: 1. How can I tell if/why my thread stopping? 2. If it's really from over processing what should I do? I really need this action to be implemented. Heres some code im using: To create the thread: [NSThread detachNewThreadSelector:@selector(startReading) toTarget:self withObject:nil]; I'll post any information you need, Thanks so much! Update I'm using GCD now and it populates the threads for me. However the OS still kills the threads. I know exactly when is it happening. when i tell my [AVplayer play]; it kills the thread. This issue is only happening in the actual iPad and not on the simulator

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  • How solve consumer/producer task using semaphores

    - by user1074896
    I have SimpleProducerConsumer class that illustrate consumer/producer problem (I am not sure that it's correct). public class SimpleProducerConsumer { private Stack<Object> stack = new Stack<Object>(); private static final int STACK_MAX_SIZE = 10; public static void main(String[] args) { SimpleProducerConsumer pc = new SimpleProducerConsumer(); new Thread(pc.new Producer(), "p1").start(); new Thread(pc.new Producer(), "p2").start(); new Thread(pc.new Consumer(), "c1").start(); new Thread(pc.new Consumer(), "c2").start(); new Thread(pc.new Consumer(), "c3").start(); } public synchronized void push(Object d) { while (stack.size() >= STACK_MAX_SIZE) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } stack.push(new Object()); System.out.println("push " + Thread.currentThread().getName() + " " + stack.size()); notify(); } public synchronized Object pop() { while (stack.size() == 0) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(50); } catch (InterruptedException e) { e.printStackTrace(); } stack.pop(); System.out.println("pop " + Thread.currentThread().getName() + " " + stack.size()); notify(); return null; } class Consumer implements Runnable { @Override public void run() { while (true) { pop(); } } } class Producer implements Runnable { @Override public void run() { while (true) { push(new Object()); } } } } I found simple realization of semaphore(here:http://docs.oracle.com/javase/tutorial/essential/concurrency/guardmeth.html I know that there is concurrency package) How I need to change code to exchange java objects monitors to my custom semaphore. (To illustrate C/P problem using semaphores) Semaphore: class Semaphore { private int counter; public Semaphore() { this(0); } public Semaphore(int i) { if (i < 0) throw new IllegalArgumentException(i + " < 0"); counter = i; } public synchronized void release() { if (counter == 0) { notify(); } counter++; } public synchronized void acquire() throws InterruptedException { while (counter == 0) { wait(); } counter--; } }

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  • How to have synchronous writing to a file (Threads) ?

    - by bobby
    Hi all. I created and started some Threads that each one writes something to a common text file. but the following error appears to me: "The process cannot access the file 'C:\hello.txt' because it is being used by another process." void AccessFile() { int num = 5; Thread[] trds = new Thread[5]; for (int i = 0; i < num; i++) { trds[i] = new Thread(new ParameterizedThreadStart(WriteToFile)); } for (int i = 0; i < num; i++) { trds[i].Start(String.Format("{0}: Hello from thread id:#{1}", i, trds[i].ManagedThreadId)); } } void WriteToFile(object message) { string FileName = "C:\\hello.txt"; string mess = (string)message; System.IO.StreamWriter sw = null; FileStream objStream = null; sw = File.AppendText(FileName); if (sw == null) { objStream = new FileStream(FileName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite); sw = new StreamWriter(objStream); } sw.WriteLine(mess); sw.Close(); sw.Dispose(); } the AccessFile() method is the starting point. could any one tell me what should i do?

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  • How to get thread status..in Multi threading..

    - by Qutbuddin Kamaal
    Hi, May be it sound dumb but if I want some computed value from other thread and other value from one more thread and this two value in my main thread how can I,if In case second thread completed before first one.it will create problem..so I just want is there any way that I can get the thread status means its still running or stop. Thanks

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  • What the best multi-thread application debugger for C++ apps.

    - by Coredumped
    I'm looking for a good multi-thread-aware debugger, capable of showing performance charts of application threads on Linux, don't know if such a thing exists, perhaps as a Eclipse plugin. The idea would be to track per thread memory allocation a CPU usage as well as being able to interrupt a thread and examine its stack trace, local vars, etc. It does not have to be an eclipse plugin or a free tool, do any of you have heard of something similar?

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  • Why aren't my threads start at the same time? Java

    - by Ada
    Hi, I have variable number of threads which are used for parallel downloading. I used this, for(int i = 0; i< sth; i++){ thrList.add(new myThread (parameters)); thrList.get(i).start(); thrList.get(i).join(); } I don't know why but they wait for each other to complete. When using threads, I am supposed get mixed print outs, since right then there are several threads running that code. However, when I print them out, they are always in order and one thread waits for the previous one to finish first. I only want them to join the main thread, not wait for each other. I noticed that when I measured time while downloading in parallel. How can I fix this? Why are they doing it in order? In my .java, there is MyThread class with run and there is Downloader class with static methods and variables. Would they be the cause of this? The static methods and variables? How can I fix this problem?

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