[petsc-dev] mpi_comm_create_group()

[Jed Brown]

Adrian Croucher <a.croucher at auckland.ac.nz> writes:

> On 12/3/21 12:09 PM, Jed Brown wrote:
>> Many find MPI_Comm_split() to be a more convenient interface.
> Yes, I don't think that will work for my case though, as my groups may 
> overlap, and some processes may not be in any group.

You'd need more calls in case of overlap (so MPI_Comm_create_group is more natural), but non-participating ranks is easy.

  | A process may supply the color value MPI_UNDEFINED, in which case newcomm returns MPI_COMM_NULL.