Thanks very much, Edgar. I will definitely go with mpi_comm_create,
then. I will need two extra scans to get set up for those operations,
but that sounds much better than an Allgather (after some reflection, I
was guessing that you would be doing an Allgather to organize the color
keys).
I
Here are the communication operations occurring in the best case
scenario in Open MPI right now:
Comm_create:
- Communicator ID allocation: 2 Allreduce operations per round of
negotiations
- 1 Allreduce operation for 'activating' the communicator
Comm_split:
- 1 Allgather operation fo
