MPI_Cart_create(3)

NAME
MPI_Cart_create - Makes a new communicator to which Cartesian topology information has been attached.

SYNTAX

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)

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

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

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).

OUTPUT PARAMETERS

comm_cart
    Communicator with new Cartesian topology (handle).

IERROR
    Fortran only: Error status (integer).

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.

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++ 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.