•MPI_COMM_WORLD
•Ability to define communicators, treat certain subsets
of processes as a communication universe
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–MPI_Group MPI_GROUP_WORLD
–MPI_Group first_row_group
–/* Create the new communicator
*/
–MPI_Comm_create(MPI_COMM_WORLD,
first_row_group,
–&first_row_comm);
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