I just started to use openmp for my code. but I can't understand the meaning of thread number.
As far as I know, the uni-processor has only one thread. however, when I tested my code varying the OMP_NUM_THREADS from 1 to 64, I can see the computational time gets smaller or sometimes larger. What's the relationship between the physical number of thread in processor and the number of OMP_NUM_THREADS ?
One more question is a little bit funny situation. When I comparedtheelasped time of openmp-codewith OMP_NUM_THREADS=64 in both uni-processor and dual-processor, surprisingly the time of uni-processor is shorter than dual-processor!!! Isn't there any person that may give me the explanation ? ( I used dual-processor linux-box for testing. For uni-processor, I rebooted my linux box without SMP kernel and tested, and for dual-processor I chose the SMP kernel and tested)
I need your help and your help will be greatly appreciated.