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