> On 2 Jun 2020, at 09:54, Matthew Knepley <[email protected]> wrote:
>
> I almost agree. I still think we do not change Distribute(), since it is
> really convenient, but we do check sizes on input as you say.
If we only want Distribute(), we have to change it a bit, because right now
there's only one communicator involved.
So one could go to
DMPlexDistribute(DM old, PetscInt overlap, MPI_Comm commNew, PetscSF *sf, DM
*new)
and commNew may be MPI_COMM_NULL, meaning we pick it up from old->comm.
> We either,
>
> 1) Copy the DM to a larger comm with empty slots on input
>
> or
>
> 2) Copy the DM to a smaller comm eliminating empty slots on output
>
> depending on P_in < P_out, or the reverse.
So we now also need to decide on the semantics of the migrationSF. I guess it
lives on commNew, but is collective over commNew \cap commOld. I can't think
through if this breaks anything.
Lawrence
