[DFTB-Plus-User] OpenMP with DFTB+

[Alessandro LANDI]

Many thanks Bálint for your quick answer.

I'll try both possibilities (binary and installation of parallelized
Lapack, I think it should be the OpenBlas library)

Best regards,
Alessandro

Il giorno gio 21 nov 2019 alle ore 18:09 Bálint Aradi <aradi at uni-bremen.de>
ha scritto:

> Dear Alessandro,
>
> Most probably, your linked LAPACK / BLAS libraries which are not
> threaded. In usual calculations DFTB+ spends over 90% of its runtime in
> the diagonalisation routine of the external library. It that is not
> threaded, you basically won't see any effects when allowing threads.
>
> Make sure, you link threaded LAPACK and BLAS implementation to the code.
>
> You could also try to use the binary from
>
> http://www.dftbplus.org/download/dftb-stable/
>
> as that is linked against a performant and threaded library.
>
> Best regards,
>
> Bálint
>
>
> On 21.11.19 14:26, Alessandro LANDI wrote:
> > Dear DFTB+ users,
> > I have a problem related the use of DFTB+ with OpenMP.
> >
> > I am using a Linux Ubuntu 14.04.6, with 8 cores.
> >
> > I have tried to run the attached input file (conjugate gradient
> > optimization of a rubrene cell with cell axes invariated) both using an
> > old DFTB+ version (1.3) and using the latest stable release (19.1), but
> > in both cases when typing the "top" command under Linux environment, I
> > get a %CPU usage of 100%, thus indicating a single thread in use.
> >
> > I have used the attached makefile to compile the DFTB+ code (I attach
> > both 1.3 and 19.1 version). I have used gfortran and gcc 7.4.0 versions.
> > I have installed blas, lapack, arpack and atlas libraries.
> > Moreover, of course I have set "export OMP_NUM_THREADS=8" in my Linux
> > environment.
> >
> > I have tried to browse the web looking for similar problems, but
> > unfortunately, I found nothing.
> >
> > Do you please have any suggestions on what I am doing wrong?
> >
> > Best regards,
> > Alessandro
> >
> > --
> > Alessandro Landi, Assegnista di Ricerca
> > Dipartimento di Chimica e Biologia "Adolfo Zambelli"
> > Università degli Studi di Salerno
> > Via Giovanni Paolo II, 132 - 84084 - Fisciano (SA)
> > Phone number 089969390
> >
> > _______________________________________________
> > DFTB-Plus-User mailing list
> > DFTB-Plus-User at mailman.zfn.uni-bremen.de
> >
> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user
> >
>
>
> --
> 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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-- 
Alessandro Landi, Assegnista di Ricerca
Dipartimento di Chimica e Biologia "Adolfo Zambelli"
Università degli Studi di Salerno
Via Giovanni Paolo II, 132 - 84084 - Fisciano (SA)
Phone number 089969390
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