17.2.37. MPI_Cart_map

MPI_Cart_map - Maps process to Cartesian topology information.

17.2.37.1. Syntax

17.2.37.1.1. C Syntax

#include <mpi.h>

int MPI_Cart_map(MPI_Comm comm, int ndims, const int dims[],
    const int periods[], int *newrank)

17.2.37.1.2. 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(*)

17.2.37.1.3. 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

17.2.37.2. 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.

17.2.37.3. 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).

17.2.37.4. 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.

17.2.37.5. 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.

See also

MPI_Graph_map