MPI_Cart_map(3)

NAME
MPI_Cart_map - Maps process to Cartesian topology information.

SYNTAX

C Syntax
#include <mpi.h>
int MPI_Cart_map(MPI_Comm comm, int ndims, const int dims[],
	const int periods[], int *newrank)

Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_CART_MAP(COMM, NDIMS, DIMS, PERIODS, NEWRANK, IERROR)
	INTEGER	COMM, NDIMS, DIMS(*), NEWRANK, IERROR
	LOGICAL	PERIODS(*)

Fortran 2008 Syntax
USE mpi_f08
MPI_Cart_map(comm, ndims, dims, periods, newrank, ierror)
	TYPE(MPI_Comm), INTENT(IN) :: comm
	INTEGER, INTENT(IN) :: ndims, dims(ndims)
	LOGICAL, INTENT(IN) :: periods(ndims)
	INTEGER, INTENT(OUT) :: newrank
	INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

comm
    Input communicator (handle).

ndims
    Number of dimensions of Cartesian structure (integer).

dims
    Integer array of size ndims specifying the number of processes in each coordinate direction.

periods
    Logical array of size ndims specifying the periodicity specification in each coordinate direction.

OUTPUT PARAMETERS

newrank
    Reordered rank of the calling process; MPI_UNDEFINED if calling process does not belong to grid (integer).

IERROR
    Fortran only: Error status (integer).

DESCRIPTION
MPI_Cart_map and MPI_Graph_map can be used to implement all other topology functions. In general they will not be called by the user directly, unless he or she is creating additional virtual topology capability other than that provided by MPI.

MPI_Cart_map computes an "optimal" placement for the calling process on the physical machine. A possible implementation of this function is to always return the rank of the calling process, that is, not to perform any reordering.

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.

SEE ALSO

MPI_Graph_map