More MPI Functions
Int MPI_Comm_split( MPI_Comm old_comm,
Creates a new communicator for each value of split_key
Processes with the same value of split key form a new group
The rank in the new group is determined by the value of rank key:
order preserving with ties arbitrated by MPI
This is a collective operation! Must call but can indicate that you
don’t want to participate by using MPI_UNDEFINED as the split key.
In that case MPI_COMM_NULL will be returned.