[Omp] number of processors vs number of threads

[mbernabeu at dsic.upv.es]

Hello everyone,

I've been executing some OpenMP code in a Xeon biprocessor. There is something
about execution times that i can't understand. Normally i use "export
OMP_THREAD_NUM=2" to ensure 1 thread it's executing on each processors.
Depending on the program and the amount of data, I'm getting better times using
OMP_THREAD_NUM=4 or OMP_THREAD_NUM=8 despite there are just 2 processors.

I supose that this is relationated whith idle times and so on. Could anyone give
me a more technical answer?

Thanks a lot.

--

M. Óscar Bernabeu i Llinares
Departament de Sistemes Informàtics i Computació.
Universitat Politècnica de València.
València. Spain.
mbernabeu at dsic.upv.es



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