MPI_Comm_test_inter(3) Open MPI MPI_Comm_test_inter(3)
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
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
INTEGER COMM, IERROR
LOGICAL FLAG
Fortran 2008 Syntax
USE mpi_f08
MPI_Comm_test_inter(comm, flag, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm
LOGICAL, INTENT(OUT) :: flag
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
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 ex-
pected values, group size, group, and rank. When dealing with an in-
ter-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 an intercommunicator: MPI_Comm_remote_size, MPI_Comm_remote_group.
The intercommunicator accessors (MPI_Comm_test_inter, MPI_Comm_re-
mote_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++ 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
4.1.2 Nov 24, 2021 MPI_Comm_test_inter(3)
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