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openmp on dual CPU (4 cores) strange behaviour on Xeon

boaz_sternfeld
Beginner
135 Views

Hey,

My executable called 'LoadLibrary' that loades a dllthat areusing OpenMP and the behaviour is good

Now I do LoadLibray to a differnt dll that also use OpenMP and the performace are going up and down.

If I use only on LoadLibrary no matter which dll it will wor fine.

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2 Replies
Om_S_Intel
Employee
135 Views
It would be nice if you can help with sample test case.
jimdempseyatthecove
Black Belt
135 Views

This sounds as both DLLs are starting there own OpenMP thread pool (for use within each respective DLL).

Try setting the KMP_BLOCK_TIME=0 (environment variable) or if your version of the OpenMP runtime library has a callable function to set the block time to 0 then try that.

Without the above, you will also experienct this problem running an application that uses OpenMP and which calls the DLL itself using a different OpenMP thread pool.

Jim Dempsey

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