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MPI_Cart_create.3.rst

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MPI_Cart_create

:ref:`MPI_Cart_create` |mdash| 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

:ref:`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 :ref:`MPI_Comm_split`. The call is erroneous if it specifies a grid that is larger than the group size.

ERRORS