[DFTB-Plus-User] DFTB+ maximum number of threads

Visikovskiy Anton anton_v at nucl.kyushu-u.ac.jp
Tue Mar 15 03:10:01 CET 2016

Dear all,

I have a little bit technical question.
I have compiled DFTB+ code using Intel Fortran compiler with OpenMP 
support (-openmp option) to allow multi-threading computation. I have 
Core i7 machine with 6 physical cores and 12 threads. However, the 
program seems to never use more then six threads. The number of threads 
used by program can be successfully controlled by OMP_NUM_THREADS 
environment variable from 1 to 6, so OpenMP seems to work fine. However, 
if I try to use more (ideally I would like to use all 12 threads to 
speed up calculations, I'm trying to work on pretty large cell), it 
never does. So, the question is, if there are hard coded limits on the 
maximum number of threads the code can use, or there is some trick to 
compilation process to make it use more than 6 threads?

Anton Visikovskiy.

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