The following are all local operations.

MPI_COMM_SIZE(comm, size) IN comm communicator OUT size number of processes in the group of commMPI_Comm_size(MPI_Comm comm, int *size)

MPI_COMM_SIZE(COMM, SIZE, IERROR)INTEGER COMM, SIZE, IERROR

MPI_COMM_SIZE returns the size of the group associated with comm.

This function indicates the number of processes involved in an intracommunicator. For MPI_COMM_WORLD, it indicates the total number of processes MPI_COMM_WORLD available at initialization time. (For this version of MPI, this is also the total number of processes available throughout the computation).

MPI_Comm_rank(MPI_Comm comm, int *rank)

MPI_COMM_RANK(COMM, RANK, IERROR)INTEGER COMM, RANK, IERROR

MPI_COMM_RANK indicates the rank of the process that calls it, in the range from 0...size-1, where size is the return value of MPI_COMM_SIZE. This rank is relative to the group associated with the intracommunicator comm. Thus, MPI_COMM_RANK(MPI_COMM_WORLD, rank) returns in rank the ``absolute'' rank of the calling process in the global communication group of MPI_COMM_WORLD; MPI_COMM_RANK( MPI_COMM_SELF, rank) returns rank = 0.

MPI_Comm_compare(MPI_Comm comm1,MPI_Comm comm2, int *result)

MPI_COMM_COMPARE(COMM1, COMM2, RESULT, IERROR)INTEGER COMM1, COMM2, RESULT, IERROR

MPI_COMM_COMPARE is used to find the relationship between
two intra-communicators. MPI_IDENT results if and only if
MPI_IDENT
comm1 and comm2 are handles for the same object
(representing the same communication domain).
MPI_CONGRUENT results if the underlying groups are identical
MPI_CONGRUENT
in constituents and rank order (the communicators
represent two distinct communication domains with the same group attribute).
MPI_SIMILAR results if the group members of both
MPI_SIMILAR
communicators are the same but the rank order
differs. MPI_UNEQUAL results otherwise. The groups
MPI_UNEQUAL
associated with two *different* communicators could be gotten via
MPI_COMM_GROUP and then used in a call to
MPI_GROUP_COMPARE. If MPI_COMM_COMPARE gives
MPI_CONGRUENT then MPI_GROUP_COMPARE will give
MPI_IDENT. If MPI_COMM_COMPARE gives
MPI_SIMILAR then MPI_GROUP_COMPARE will give
MPI_SIMILAR.

Fri Sep 1 06:16:55 EDT 1995