[petsc-dev] attaching field information to PetscLayout?

[Jed Brown]

On Sat, May 14, 2011 at 21:47, Dmitry Karpeev <karpeev at mcs.anl.gov> wrote:

> Can these split ISs have communicators different from that of
> PetscLayout (this is something I use in GASM,
> for example)?
>

I guess I always thought of the field information in PetscLayout as having
semantic meaning to the user. I also thought these ISs would be strictly
non-overlapping and addressing locally owned values. In that context, there
is no particular disadvantage to always using global ISs, and I think it
would help keep the code simple. If you are going to solve part of the
problem on a sub-communicator, you can define that subcomm as all those
processes that have non-empty local part in the IS. If you have a huge
number of splits (such that individual splits on longer have semantic
meaning), then I think it is a different purpose.
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