Adrian Croucher <[email protected]> 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.