[CPMD-list] MPI or OpenMP

[Juerg Hutter]

Hi

> Dear CPMD users/authors,
>
> I do my calculations on 64 CPU HP SuperDome machine using MPI version. Because that machine is SMP, I am wondering: what is the best - to use mpi version or use OpenMP versions or use mixed MPI/OpenMP ?

The optimal parallel setup will depend on the system you want to
calculate. However, there are some general rules that
apply.

SMP performance levels off between 4 and 8 CPUs, on some machines even
between 2 and 4.
MPI performance is superior usually up to N/2, where N is
the number of grid points in x direction.

For most systems and cutoffs N will be between 64 and 256.

Therefore, in your case the MPI version will be most likely
most efficient.

Juerg Hutter





>
> Thank you very much,
>   Best wishes,
>     Sergey
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