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 return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_INIT / MPI_INIT_THREAD, after MPI_FINALIZE, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_COMM_SET_ERRHANDLER on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_COMM_SPAWN[_MULTIPLE]. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

In the sessions model, the error handler can be set during MPI_Session_init.

Open MPI includes three predefined error handlers that can be used:

MPI_ERRORS_ARE_FATAL: Causes the program to abort all connected MPI processes.
MPI_ERRORS_ABORT:     An error handler that can be invoked on a communicator,
                      window, file, or session. When called on a communicator, it
                      acts as if MPI_ABORT was called on that communicator. If
                      called on a window or file, acts as if MPI_ABORT was called
                      on a communicator containing the group of processes in the
                      corresponding window or file. If called on a session,
                      aborts only the local process.
MPI_ERRORS_RETURN:    Returns an error code to the application.

MPI applications can also implement their own error handlers.

Custom MPI error handlers can be created by calling: MPI_Comm_create_errhandler(3) MPI_File_create_errhandler(3) MPI_Session_create_errhandler(3) MPI_Win_create_errhandler(3)

Predefined and custom error handlers can be set by calling: MPI_Comm_set_errhandler(3) MPI_File_set_errhandler(3) MPI_Session_set_errhandler(3) MPI_Win_set_errhandler(3)

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3 standard for more information.

See also

MPI_Graph_map