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

Bálint Aradi aradi at uni-bremen.de
Tue Mar 15 08:14:19 CET 2016

Dear Anton,

> 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?

We do not impose any hard coded limit on the number of threads.
Actually, most threaded activity happens within MKL itself, so it is
MKL, which apparently refuses to use more threads. But the question is
really, does your machine recognise 6 or 12 threads? Usually MKL
launches as many threads, as the OS reports cores on the machine.

  Best regards,


Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen

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