[DFTB-Plus-User] Running DFTB+17.1 executables in multi-threads

[Bálint Aradi]

Dear Wanryun,

> In previous versions, export OMP_NUM_THREADS=n could be used to set 
> the threads (cores) but it seems not working for the 17.1. The jobs 
> always drop to a single-thread running though fluctuations of CPU 
> occupations over 1 occurs occasionally.
> 
> Besides, in previous versions, no specification of threads will make 
> a job occupy all the threads of the node, but the default running of 
> the 17.1 version now only takes 1 thread.

Now, that the DFTB+ binary can be downloaded by anybody without
registration, there are some legal constraints (mainly US export
restrictions) on the compiler and libraries we can use for building the
public binary. This restricts us basically to open source compilers and
libraries only.

The public binary on the website has been compiled with GNU Fortran and
linked against the OpenBLAS library. OpenBLAS is threaded and you still
can use the OMP_NUM_THREADS environment variable to control the number
of threads. However, the threading of the diagonalisation routines in
OpenBLAS is unfortunately poor, this is why most of the time you see
less load/threads than possible.

As stated on the website, you can obtain a much more performant and
better scaling binary, if you compile the source yourself, using Intels
Fortran compiler and (even more important) by linking it against the
Intel MKL library. You find an appropriate makefile in the sys/ folder,
so it should be quite straightforward, provided you have access to those
compilers and libraries.

  Best regards,

  Bálint

-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/


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