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MPI_Comm_test_inter(3) man page (version 1.8.4)

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Table of Contents

Name

MPI_Comm_test_inter - Tests to see if a comm is an intercommunicator.

Syntax

C Syntax


#include <mpi.h>
int MPI_Comm_test_inter(MPI_Comm comm, int *flag)

Fortran Syntax


INCLUDE ’mpif.h’
MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
    INTEGER    COMM, IERROR
    LOGICAL    FLAG

C++ Syntax


#include <mpi.h>
bool Comm::Is_inter() const

Input Parameter

comm
Communicator (handle).

Output Parameters

flag (Logical.)
IERROR
Fortran only: Error status (integer).

Description

This local routine allows the calling process to determine the type of a communicator. It returns true for an intercommunicator, false for an intracommunicator.

The type of communicator also affects the value returned by three other functions. When dealing with an intracommunicator (enables communication within a single group), the functions listed below return the expected values, group size, group, and rank. When dealing with an inter-communicator, however, they return the following values:


MPI_Comm_size    Returns the size of the local group.
MPI_Comm_group    Returns the local group.
MPI_Comm_rank    Returns the rank in the local group.

To return the remote group and remote group size of an inter-communicator, use the MPI_Comm_remote_group and MPI_Comm_remote_size functions.

The operation MPI_Comm_compare is valid for intercommunicators. Both communicators must be either intra- or intercommunicators, 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 intercommunicator: MPI_Comm_remote_size, MPI_Comm_remote_group.

The intercommunicator accessors (MPI_Comm_test_inter, MPI_Comm_remote_size, MPI_Comm_remote_group) are all local operations.

Errors

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.

Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

See Also


MPI_Comm_remote_group
MPI_Comm_remote_size
MPI_Intercomm_create
MPI_Intercomm_merge

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