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MPI_Comm_test_inter - Tests to see if a comm is an intercommunicator.
#include <mpi.h>
int MPI_Comm_test_inter(MPI_Comm comm, int *flag)
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_COMM_TEST_INTER(COMM, FLAG, IERROR)
INTEGER COMM, IERROR
LOGICAL FLAG
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
- comm
- Communicator (handle).
- flag (Logical.)
- IERROR
- Fortran only: Error status (integer).
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.
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.
MPI_Comm_remote_group
MPI_Comm_remote_size
MPI_Intercomm_create
MPI_Intercomm_merge
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