An MPI communicator specifies the communication context for a communication operation. In particular, it specifies the set of processes which share the context, and assigns each each process a unique rank (see
MPI.Comm_rank) taking an integer value in
n is the number of processes in the communicator (see
A communicator containing all processes with which the local rank can communicate at initialization. In a typical "static-process" model, this will be all processes.
A communicator containing only the local process.
The total number of available slots, or
nothing if it is not defined. This is determined by the
MPI_UNIVERSE_SIZE attribute of
This is typically dependent on the MPI implementation: for MPICH-based implementations, this is specified by the
-usize argument. OpenMPI defines a default value based on the number of processes available.