Feature #1060: AMPI compliance with MPI-3.1 standard
AMPI support for MPI-3's MPI_Comm_create_group
#2 Updated by Sam White about 3 years ago
It looks like in the current method of group creation for MPI_Comm_create() all members of the input communicator contribute to a reduction, which then triggers the root of that reduction to create the new communicator. This should look like an Reduce_scatter or Allreduce. If the group is MPI_GROUP_EMPTY, then just set newcomm to MPI_COMM_NULL, do a no-op contribution to the reduction on the input comm and return. If the group is a subgroup of the input comm, give a valid contribution to the reduction to create the new group and wait on a message from the root of that reduction.