[petsc-dev] mpi_comm_create_group()

[Adrian Croucher]

On 12/3/21 5:31 PM, Jed Brown wrote:
> 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.

Ah, interesting. I guess mpi_comm_split() might also have the advantage 
that each rank only needs to know if it is in the group or not, rather 
than needing an array of all participating ranks, as mpi_comm_create() 
and mpi_comm_create_group() do.

- Adrian

-- 
Dr Adrian Croucher
Senior Research Fellow
Department of Engineering Science
University of Auckland, New Zealand
email: a.croucher at auckland.ac.nz
tel: +64 (0)9 923 4611