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MPI_Cart_sub - Partitions a communicator into subgroups, which
form lower-dimensional Cartesian subgrids.
#include <mpi.h>
int MPI_Cart_sub(MPI_Comm comm, const int remain_dims[], MPI_Comm *comm_new)
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_CART_SUB(COMM, REMAIN_DIMS, COMM_NEW, IERROR)
INTEGER COMM, COMM_NEW, IERROR
LOGICAL REMAIN_DIMS(*)
USE mpi_f08
MPI_Cart_sub(comm, remain_dims, newcomm, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm
LOGICAL, INTENT(IN) :: remain_dims(*)
TYPE(MPI_Comm), INTENT(OUT) :: newcomm
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- comm
- Communicator with Cartesian structure (handle).
- remain_dims
- The ith entry of remain_dims specifies whether the ith dimension is kept
in the subgrid (true) or is dropped (false) (logical vector).
- comm_new
- Communicator containing the subgrid that includes the calling process (handle).
- IERROR
- Fortran only: Error status (integer).
If a Cartesian
topology has been created with MPI_Cart_create, the function MPI_Cart_sub
can be used to partition the communicator group into subgroups that form
lower-dimensional Cartesian subgrids, and to build for each subgroup a communicator
with the associated subgrid Cartesian topology. (This function is closely
related to MPI_Comm_split.)
Example: Assume that MPI_Cart_create( ..., comm)
has defined a (2 x 3 x 4) grid. Let remain_dims = (true, false, true).
Then a call to
MPI_Cart_sub(comm, remain_dims, comm_new)
will create three communicators, each with eight processes in a 2 x 4 Cartesian
topology. If remain_dims = (false, false, true) then the call to MPI_Cart_sub(comm,
remain_dims, comm_new) will create six nonoverlapping communicators, each
with four processes, in a one-dimensional Cartesian topology.
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_Cart_create
MPI_Comm_split
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