Intel® MPI Benchmarks User Guide and Methodology Description

# Communicators, Active Processes

Communicator management is repeated in every "`select MY_COMM`" step. If it exists, the previous communicator is freed. When you run `Q<=P` processes, the first `Q` ranks of `MPI_COMM_WORLD` are put into one group, and the remaining `P-Q` get `MPI_COMM_NULL`.

The group of `MY_COMM` calls the active processes group.