137. Inter-communicator Accessors

MPI_COMM_TEST_INTER(comm, flag)
IN comm	communicator (handle)
OUT flag	(logical)

int MPI_Comm_test_inter(MPI_Comm comm, int *flag)

MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
INTEGER COMM, IERROR
LOGICAL FLAG
bool MPI::Comm::Is_inter() const
This local routine allows the calling process to determine if a communicator is an inter-communicator or an intra-communicator. It returns true if it is an inter-communicator, otherwise false.

When an inter-communicator is used as an input argument to the communicator accessors described above under intra-communication, the following table describes behavior.

Furthermore, the operation MPI_COMM_COMPARE is valid for inter-communicators. Both communicators must be either intra- or inter-communicators, or else MPI_UNEQUAL results. Both corresponding local and remote groups must compare correctly to get the results MPI_CONGRUENT and MPI_SIMILAR. In particular, it is possible for MPI_SIMILAR to result because either the local or remote groups were similar but not identical.

The following accessors provide consistent access to the remote group of an inter-communicator:

The following are all local operations.

MPI_COMM_REMOTE_SIZE(comm, size)
IN comm	inter-communicator (handle)
OUT size	number of processes in the remote group of comm (integer)

int MPI_Comm_remote_size(MPI_Comm comm, int *size)

MPI_COMM_REMOTE_SIZE(COMM, SIZE, IERROR)
INTEGER COMM, SIZE, IERROR
int MPI::Intercomm::Get_remote_size() const

MPI_COMM_REMOTE_GROUP(comm, group)
IN comm	inter-communicator (handle)
OUT group	remote group corresponding to comm (handle)

int MPI_Comm_remote_group(MPI_Comm comm, MPI_Group *group)

MPI_COMM_REMOTE_GROUP(COMM, GROUP, IERROR)
INTEGER COMM, GROUP, IERROR
MPI::Group MPI::Intercomm::Get_remote_group() const

Rationale.

Symmetric access to both the local and remote groups of an inter-communicator is important, so this function, as well as MPI_COMM_REMOTE_SIZE have been provided. ( End of rationale.)