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

[boaz_sternfeld]

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.

[Om_S_Intel]

It would be nice if you can help with sample test case.

[jimdempseyatthecove]

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