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• Registering an event from different thread

  - by ET

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

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• Execution issue with PyModule_AddIntConstant function

  - by karnol

  I m learning python c api functions and keen to learn python 3.1 stable version. Found an unresolved issue recently and tried PyModule_AddIntConstant(PyObject *module, const char *name, long value) Runtime error occurred for this function call. Is there something wrong with the function in python 3.1?

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• how to use CreateThread for functions which are class members

  - by jeromekjeromepune

  how to use CreateThread() to create threads of functions which are class members.

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• Thread help with Android game

  - by Ciph3rzer0

  I need some help dealing with three Threads in Android One thread is the main thread, the other is the GLThread, and the other is a WorkerThread I created to update the game state. The problem I have is they all need to access the same LinkedList of game objects. Both the GLThread and my WorkerThread only read from the LinkedList, so no problem there, but occasionally I have the main thread adding in another game object to the list. How can I manage this? I tried using synchronized in front of the functions involved but it really slows down the application. For some reason, just catching the errors and not rendering or updating the game state that frame, causes it to start lagging permanently. Anyone have any great ideas?

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• New form on a different thread

  - by Dan

  So I have a thread in my application, which purpose is to listen to messages from the server and act according to what it recieves. I ran into a problem when I wanted to fire off a message from the server, that when the client app recieves it, the client app would open up a new form. However this new form just freezes instantly. I think what's happening is that the new form is loaded up on the same thread as the thread listening to the server, which of course is busy listening on the stream, in turn blocking the thread. Normally, for my other functions in the clients listening thread, I'd use invokes to update the UI of the main form, so I guess what I'm asking for is if here's a way to invoke a new form on the main form.

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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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• std::thread and class constructor and destructor

  - by toeplitz

  When testing threads in C++11 I have created the following example: #include <iostream> #include <thread> class Foo { public: Foo(void) { std::cout << "Constructor called: " << this << std::endl; } ~Foo(void) { std::cout << "Destructor called: " << this << std::endl; } void operator()() const { std::cout << "Operatior called: " << this << std::endl; } }; void test_normal(void) { std::cout << "====> Standard example:" << std::endl; Foo f; } void test_thread(void) { std::cout << "====> Thread example:" << std::endl; Foo f; std::thread t(f); t.detach(); } int main(int argc, char **argv) { test_normal(); test_thread(); for(;;); } Which prints the following: Why is the destructor called 6 times for the thread? And why does the thread report different memory locations?

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• Reason for unintuitive UnboundLocalError behaviour 2

  - by Jonathan

  Following up on Reason for unintuitive UnboundLocalError behaviour (I will assume you've read it). Consider the following Python script: def f(): # a+=1 # 1 aa=a aa+=1 # b+='b' # 2 bb=b bb+='b' c[0]+='c' # 3 c.append('c') cc=c cc.append('c') # 4 a=1 b='b' c=['c'] f() print a print b print c The result of the script is: 1 b ['cc', 'c', 'c'] The commented out lines (marked 1,2) are lines that would through an UnboundLocalError and the SO question I referenced explains why. However, the line marked 3 works! By default, lists are copied by reference in Python, therefore it's understandable that c changes when cc changes. But why should Python allow c to change in the first place, if it didn't allow changes to a and b directly from the method's scope? I don't see how the fact that by default lists are copied by reference in Python should make this design decision inconsistent. What am I missing folks?

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

  - by user65374

  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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• Is there a straightforward way to have a ThreadStatic instance member?

  - by Dan Tao

  With the ThreadStatic attribute I can have a static member of a class with one instance of the object per thread. This is really handy for achieving thread safety using types of objects that don't guarantee thread-safe instance methods (e.g., System.Random). It only works for static members, though. Is there some corresponding attribute that provides the same functionality, but for instance members? In other words, that allows me to have one instance of the object, per thread, per instance of the containing class?

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• .NET Threading : How to wait for other thread to finish some task

  - by Alex Ilyin

  Assume I have method void SomeMethod(Action callback) This method does some work in background thread and then invokes callback. The question is - how to block current thread until callback is called ? There is an example bool finished = false; SomeMethod(delegate{ finished = true; }); while(!finished) Thread.Sleep(); But I'm sure there should be better way

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• Java - multithreaded access to a local value store which is periodically cleared

  - by Telax

  I'm hoping for some advice or suggestions on how best to handle multi threaded access to a value store. My local value storage is designed to hold onto objects which are currently in use. If the object is not in use then it is removed from the store. A value is pumped into my store via thread1, its entry into the store is announced to listeners, and the value is stored. Values coming in on thread1 will either be totally new values or updates for existing values. A timer is used to periodically remove any value from the store which is not currently in use and so all that remains of this value is its ID held locally by an intermediary. Now, an active element on thread2 may wake up and try to access a set of values by passing a set of value IDs which it knows about. Some values will be stored already (great) and some may not (sadface). Those values which are not already stored will be retrieved from an external source. My main issue is that items which have not already been stored and are currently being queried for may arrive in on thread1 before the query is complete. I'd like to try and avoid locking access to the store whilst a query is being made as it may take some time.

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• Start and run a class member function in background, in QT/C++

  - by Regof

  Once a minute I want to run a task, not blocking other GUI functions. I heared somthing about QConcurent::run ... Or should I use signals and slots?

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• C++ boost thread reusing threads

  - by aaa

  hi. I am trying to accomplish something like this: thread t; // create/initialize thread t.launch(); // launch thread. t.wait(); // wait t.launch(); // relaunch the same thread How to go about implementing something like this using boost threads? in essence, I need persistent relaunch-able thread. Thanks

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• BlackBerry threading model

  - by Rory Fitzpatrick

  I've read a lot of comments mention in passing that the BlackBerry threading model deviates from the Java standard and can cause issues, but no amount of googling has enlightened me on what this means exactly. I've been developing a fairly large business application for the BlackBerry and, although I don't really have any previous experience with Java multi-threaded applications, haven't come across any issue that we've been able to blame on threading, other than what we caused ourselves. Can someone describe exactly how the BlackBerry threading model is different, and how I as a developer should take that into account? Obviously any links on the topic would also be great.

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• ConcurrenctBag(Of MyType) Vs List(Of MyType)

  - by Ben

  What is the advantage of using a ConcurrentBag(Of MyType) against just using a List(Of MyType)? The MSDN page on the CB (http://msdn.microsoft.com/en-us/library/dd381779(v=VS.100).aspx) states that ConcurrentBag(Of T) is a thread-safe bag implementation, optimized for scenarios where the same thread will be both producing and consuming data stored in the bag So what is the advantage? I can understand the advantage of the other collection types in the Concurrency namespace, but this one puzzled me. Thanks.

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• Timer C#. Start, stop, and get the amount of time between the calls

  - by user1886060

  I'm writing UDP chat with reliable data transfer. I need to start a timer when a packet is sent, and stop it as soon it receives an answer from the server(ACK- acknowledgment). Here is my code: private void sendButton_Click(object sender, EventArgs e) { Packet snd = new Packet(ack, textBox1.Text.Trim()); textBox1.Text = string.Empty; Smsg = snd.GetDataStream();//convert message into array of bytes to send. while (true) { try { // Here I need to Start a timer! clientSock.SendTo(Smsg, servEP); clientSock.ReceiveFrom(Rmsg, ref servEP); //Here I need to stop a timer and get elapsed amount of time. Packet rcv = new Packet(Rmsg); if (Rmsg != null && rcv.ACK01 != ack) continue; if (Rmsg != null && rcv.ACK01 == ack) { this.displayMessageDelegate("ack is received :"+ack); ChangeAck(ack); break; } Thank you.

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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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• 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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• 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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• Threading and iterating through changing collections

  - by adamjellyit

  In C# (console app) I want to hold a collection of objects. All objects are of same type. I want to iterate through the collection calling a method on each object. And then repeat the process continuously. However during iteration objects can be added or removed from the list. (The objects themselves will not be destroyed .. just removed from the list). Not sure what would happen with a foreach loop .. or other similar method. This has to have been done 1000 times before .. can you recommend a solid approach?

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• Best approach to synchronising properties across threads

  - by user290796

  Hi, I'm looking for some advice on the best approach to synchronising access to properties of an object in C++. The application has an internal cache of objects which have 10 properties. These objects are to be requested in sets which can then have their properties modified and be re-saved. They can be accessed by 2-4 threads at any given time but access is not intense so my options are: Lock the property accessors for each object using a critical section. This means lots of critical sections - one for each object. Return copies of the objects when requested and have an update function which locks a single critical section to update the object properties when appropriate. I think option 2 seems the most efficient but I just want to see if I'm missing a hidden 3rd option which would be more appropriate. Thanks, J

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• Waiting for a submitted job to finish in Oracle PL/SQL?

  - by vicjugador

  I'm looking for the equivalent of Java's thread.join() in PL/SQL. I.e. I want to kick off a number of jobs (threads), and then wait for them to finish. How is this possible in PL/SQL? I'm thinking of using dbms_job.submit (I know it's deprecated). dbms_scheduler is also an alternative. My code: DECLARE jobno1 number; jobno2 number; BEGIN dbms_job.submit(jobno1,'begin dbms_lock.sleep(10); dbms_output.put_line(''job 1 exit'');end;'); dbms_job.submit(jobno2,'begin dbms_lock.sleep(10); dbms_output.put_line(''job 2 exit'');end;'); dbms_job.run(jobno1); dbms_job.run(jobno2); //Need code to Wait for jobno1 to finish //Need code to Wait for jobno2 to finish END;

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• Keeping track of threads when creating them recursively

  - by 66replica

  I'm currently working on some code for my Programming Languages course. I can't post the code but I'm permitted to talk about some high level concepts that I'm struggling with and receive input on them. Basically the code is a recursive DFS on a undirected graph that I'm supposed to convert to a concurrent program. My professor already specified that I should create my threads in the recursive DFS method and then join them in another method. Basically, I'm having trouble thinking of how I should keep track of the threads I'm creating so I can join all of them in the other method. I'm thinking an array of Threads but I'm unsure how to add each new thread to the array or even if that's the right direction.

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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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