Alternative method for MultiThreading (insted of CWinThread in VC++)

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HI to all,
I am using CWinThread for streaming video from webcam remotely,so while creating and terminating thread I am getting errors(RunTime Error).It is creating successfully for first time,but when I am creating thread continuosly in timer after sometime I am suppose to get error and also while exiting my application I am getting errors the thread is not terminating properly.Can anyone help me out from this problem.Is there any other way instead of multithreading.If no alternative method can anyone help me out how to create and terminate thread properly.Thanks to all in advance.

Regards,
RamyaRaj

Posted 19-May-11 19:10pm

RamyaRaj from NewDelhi

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Sergey Alexandrovich Kryukov · Answer 1 · 2011-05-19T19:49:00

Solution 1

You need thread and you don't need alternative to thread, you need alternative to timer! Creating a thread by timer is a typical mistake, not very frequent though. Chances are, you need just one additional thread for whole run-time, only you should throttle it using even wait handle or some other synchronization primitive to keep your thread in wait state (spending zero CPU time for the wait) until it is given a job.

This is the idea. Unfortunately, I cannot give you more detail because you did not share your code or any relevant detail on your operation.

Don't even play with the idea of going without threads!
Get rid of your timer. Timers are evil.

—SA

Posted 19-May-11 19:49pm

Sergey Alexandrovich Kryukov

Comments

RamyaRaj from NewDelhi 20-May-11 2:17am

hi SAKryukov,

I used AfxBeginThread to create thread.

CWinThread* m_ThRecieveImage;
m_ThRecieveImage = AfxBeginThread(RecieveImage,m_CamNo,THREAD_PRIORITY_NORMAL,0,0,NULL);

I am using 16 cameras for each camera i am creating one like this.And in timer also i am calling this continuosly.

Can you please help me out from this problem.

Regards,
RamyaRaj.

Albert Holguin 20-May-11 10:59am

when are you creating the threads? when the timer is called? are you loading all the threads on the same member pointer? if so, what's the use? you're overriding your reference to that thread.

Sergey Alexandrovich Kryukov 20-May-11 23:20pm

Yes, good point.
And still no point to use a timer. Makes no sense.
--SA

RamyaRaj from NewDelhi 21-May-11 5:27am

hi Sakryukov,
Now i removed timer in my code.I am creating thread for each camera is it anything wrong.

Regards,
RamyaRaj.

RamyaRaj from NewDelhi 21-May-11 5:34am

hi Albert Holguin,
I created Pointer variable Seperately for all threads.I made a mistake of using timers,now i removed timer.But how to terminate thread and how to find wheather thread is terminated properly or not.While exiting my application i am suspending thread and terminating it but still its not terminating.Is there any other way to terminate thread.Here is the code what i used.

here m_iCamNo is camera number(I used 16 cameras).
if(m_ThRecieveImage[m_iCamNo]) m_ThRecieveImage[m_iCamNo]->SuspendThread();

::TerminateThread(m_ThRecieveImage[m_iCamNo],90);

Is there any thing wrong in that.

Thanks in advance.

Regards,
RamyaRaj.

Albert Holguin · Answer 2 · 2011-05-20T04:58:00

Solution 2

You need to sit and go through a tutorial on multithreading and using AfxBeginThread. Post a bit of code and we'll give you some advice as to what you're doing wrong, but you really need to learn about how to properly multithread first.

Posted 20-May-11 4:58am

Albert Holguin

Comments

RamyaRaj from NewDelhi 21-May-11 5:47am

hi Albert Holguin, I created Pointer variable Seperately for all threads.I made a mistake of using timers,now i removed timer.But how to terminate thread and how to find wheather thread is terminated properly or not.While exiting my application i am suspending thread and terminating it but still its not terminating.Is there any other way to terminate thread.Here is the code what i used. here m_iCamNo is camera number(I used 16 cameras). if(m_ThRecieveImage[m_iCamNo]) m_ThRecieveImage[m_iCamNo]->SuspendThread(); ::TerminateThread(m_ThRecieveImage[m_iCamNo],90);
Is there any thing wrong in that. Thanks in advance.
Regards, RamyaRaj.

Albert Holguin 22-May-11 16:35pm

that's not the proper way to terminate a thread, like I said, read a tutorial before you start using them

RamyaRaj from NewDelhi 23-May-11 0:35am

Ok Albert Holguin,
To terminate thread can i use WaitForSingleObject function

Albert Holguin 24-May-11 14:17pm

WaitForSingleObject just waits for a signal to occur, it can be used to wait for a worker thread to finish on its own... if you use a user interface thread based on CWinThread, then you typically ask the thread to stop what it's doing and exit (using a PostMessage(WM_QUIT)), then wait for it to finish with a WaitForSingleObject() on the thread handle.

RamyaRaj from NewDelhi 1-Jun-11 1:24am

hi Albert Holguin,
If I use PostMessage(WM_QUIT) it will post that message to process or thread.If it process to thread then this PostMessage will send message to which thread ,because I am using 16 threads one for each camera.Can you please help me out.Thanks in Advance.

Regards,
RamyaRaj.

Albert Holguin 1-Jun-11 9:45am

PostMessage(WM_QUIT) if for a thread, but since a process is derived from a thread, I assume it'll have the same effect on a process... As far as how do you know which one, well, if you use ::PostMessage() you have to specify the hwnd handle, that would tell the framework where to send the message, if you use CWnd::PostMessage(), you can do it directly to a any CWnd derived object, for example MyCWnd->PostMessage(WM_QUIT).

RamyaRaj from NewDelhi 2-Jun-11 1:19am

ok , If I use PostMessage(WM_QUIT) then there is no need of using WaitForSingleObject or Terminatethread to termintae the thread.

Albert Holguin 2-Jun-11 20:07pm

Actually, you still have to use WaitForSingleObject()... why? because that's how you know if the thread actually did what you asked it... otherwise you may end up with a zombie thread that doesn't go down and meanwhile your application finished (at least the GUI did)... the WaitForSingleObject() call is merely a synchronization tool