17.2.35. MPI_Cart_create
MPI_Cart_create - Makes a new communicator to which Cartesian topology information has been attached.
17.2.35.1. Syntax
17.2.35.1.1. C Syntax
#include <mpi.h>
int MPI_Cart_create(MPI_Comm comm_old, int ndims, const int dims[],
const int periods[], int reorder, MPI_Comm *comm_cart)
17.2.35.1.2. Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_CART_CREATE(COMM_OLD, NDIMS, DIMS, PERIODS, REORDER,
COMM_CART, IERROR)
INTEGER COMM_OLD, NDIMS, DIMS(*), COMM_CART, IERROR
LOGICAL PERIODS(*), REORDER
17.2.35.1.3. Fortran 2008 Syntax
USE mpi_f08
MPI_Cart_create(comm_old, ndims, dims, periods, reorder, comm_cart, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm_old
INTEGER, INTENT(IN) :: ndims, dims(ndims)
LOGICAL, INTENT(IN) :: periods(ndims), reorder
TYPE(MPI_Comm), INTENT(OUT) :: comm_cart
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
17.2.35.2. Input Parameters
comm_old
: Input communicator (handle).ndims
: Number of dimensions of Cartesian grid (integer).dims
: Integer array of size ndims specifying the number of processes in each dimension.periods
: Logical array of size ndims specifying whether the grid is periodic (true) or not (false) in each dimension.reorder
: Ranking may be reordered (true) or not (false) (logical).
17.2.35.3. Output Parameters
comm_cart
: Communicator with new Cartesian topology (handle).IERROR
: Fortran only: Error status (integer).
17.2.35.4. Description
MPI_Cart_create returns a handle to a new communicator to which the
Cartesian topology information is attached. If reorder
= false then
the rank of each process in the new group is identical to its rank in
the old group. Otherwise, the function may reorder
the processes
(possibly so as to choose a good embedding of the virtual topology onto
the physical machine). If the total size of the Cartesian grid is
smaller than the size of the group of comm, then some processes are
returned MPI_COMM_NULL, in analogy to MPI_Comm_split. The call
is erroneous if it specifies a grid that is larger than the group size.
17.2.35.5. Errors
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. 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.