[QE-users] QE6.8: "Slab decomposition and task groups not implemented"

[Paolo Giannozzi]

On Mon, Aug 16, 2021 at 3:04 PM Sebastian Hütter <sebastian.huetter at ovgu.de>
wrote:

>
> From the source code, I think "-ntg" now requires switching from slab to
> pencil decomposition using the
> undocumented switch "-pd"?
>

exactly so

>
> What are the implications of this method selection? Is one "better" or
> "worse" than the other, whatever that might mean?
>

-pd true -ntg N is the same as -ntg N in previous versions. It is
convenient only when you parallelize FFTs over a large number of MPI
processes. Otherwise, FFTs with -pd true ("pencil decomposition") are
typically slower than the default ("slab decomposition"). The choice will
be made automatic sooner or later.

Paolo


>
>
> Thanks for any help,
>
> Sebastian
>
> --
> M.Sc. Sebastian Hütter
> Otto-von-Guericke University Magdeburg
> Institute of Materials and Joining Technology
> Universitätsplatz 2
> D-39106 Magdeburg
> Tel.: +49 (0)391-67-54566
> Fax: +49 (0)391-67-44569
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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