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question about a multithreaded program

Started by theScore Jul 14, 2008 at 9:42 AM 2 replies 600+ views

Original Post

Jul 14, 2008 at 9:42 AM

Hi, I have two programs : -the first for which the threads are executed on one processor -the second for which the threads are executed on 4 processor the threads are all the same, a long but simple calculation. The question is why both programs run in 20 seconds because one optimized for a quad core ? [Edited by - theScore on July 14, 2008 9:58:52 AM]

janta

Jul 14, 2008 at 9:54 AM

It's not necessary to manually bind threads to cores to take advantage of cores (in fact, it's even considered bad). When run on a quad core machine, windows will dispatch all threads to the available core so that's why both programs run in about the same time.

theScore

Author

theScore

Jul 14, 2008 at 9:58 AM

ok thanks !

janta

Jul 14, 2008 at 11:06 AM

What you want to try to see the difference is: (pseudocode)

// multithreaded versionProfileStart();BeginThread(func1);BeginThread(func2);BeginThread(func3);func4(); // Or: BeginThread(func4);WaitUntilDone();ProfileEnd();//single threaded versionProfileStart();func1();func2();func3();func4();ProfileEnd();

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