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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 communica-
tion 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-communica-
tor, 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 the function and Fortran routines in the last argument. C++ func-
tions 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
Open MPI 1.2 September 2006 MPI_Comm_test_inter(3OpenMPI)
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