[petsc-users] Correlation between da_refine and pg_mg_levels

[Jed Brown]

Justin Chang <jychang48 at gmail.com> writes:

> It was sort of arbitrary. I want to conduct a performance spectrum
> (dofs/sec) study where at least 1k processors are used on various HPC
> machines (and hopefully one more case with 10k procs). Assuming all
> available cores on these compute nodes (which I know is not the greatest
> idea here), 1032 Ivybridge (24 cores/node) on Edison best matches Cori's
> 1024 Haswell (32 core/node).
>
> How do I determine the shape of the DMDA? I am guessing the number of MPI
> processes needs to be compatible with this?

Running with -dm_view gives you the ownership by process.  DMDA is
supposed to be tolerant of relatively weird numbers of processes and in
any case, should error in an understandable way.  1032 has a prime
factor of 43 which, with only 80 elements in a decomposed dimension,
means that some processes must have only one element in that direction.
Of course this hasn't been a problem at smaller scale.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 832 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20170402/70236a3f/attachment.pgp>