mpi_cart_map(3openmpi) [osx man page]

MPI_Cart_map(3OpenMPI)													    MPI_Cart_map(3OpenMPI)

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, int *dims,
	    int *periods, int *newrank)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_CART_MAP(COMM, NDIMS, DIMS, PERIODS, NEWRANK, IERROR)
	    INTEGER   COMM, NDIMS, DIMS(*), NEWRANK, IERROR
	    LOGICAL   PERIODS(*)

C++ Syntax
       #include <mpi.h>
       int Cartcomm::Map(int ndims, const int dims[],
	    const bool periods[]) const

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++ func-
       tions 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

Open MPI 1.2							  September 2006					    MPI_Cart_map(3OpenMPI)

MPI_Dims_create(3OpenMPI)												 MPI_Dims_create(3OpenMPI)

NAME

       MPI_Dims_create	- Creates a division of processors in a Cartesian grid.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Dims_create(int nnodes, int ndims, int *dims)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_DIMS_CREATE(NNODES, NDIMS, DIMS, IERROR)
	    INTEGER   NNODES, NDIMS, DIMS(*), IERROR

C++ Syntax
       #include <mpi.h>
       void Compute_dims(int nnodes, int ndims, int dims[])

INPUT PARAMETERS

       nnodes	 Number of nodes in a grid (integer).

       ndims	 Number of Cartesian dimensions (integer).

IN
/OUT PARAMETER
       dims	 Integer array of size ndims specifying the number of nodes in each dimension.

OUTPUT PARAMETER

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       For Cartesian topologies, the function MPI_Dims_create helps the user select a balanced distribution of processes per coordinate direction,
       depending on the number of processes in the group to be balanced and optional constraints that can be specified by the user. One use is	to
       partition all the processes (the size of MPI_COMM_WORLD's group) into an n-dimensional topology.

       The  entries  in  the array dims are set to describe a Cartesian grid with ndims dimensions and a total of nnodes nodes. The dimensions are
       set to be as close to each other as possible, using an appropriate divisibility algorithm. The caller may further constrain  the  operation
       of  this  routine  by  specifying elements of array dims. If dims[i] is set to a positive number, the routine will not modify the number of
       nodes in dimension i; only those entries where  dims[i] = 0 are modified by the call.

       Negative input values of dims[i] are erroneous. An error will occur if nnodes is not a multiple of ((pi) over (i, dims[i] != 0)) dims[i].

       For dims[i] set by the call, dims[i] will be ordered in	nonincreasing  order.  Array  dims  is	suitable  for  use  as	input  to  routine
       MPI_Cart_create. MPI_Dims_create is local.

       Example:

       dims
       before			     dims
       call	 function call	     on return
       -----------------------------------------------------
       (0,0)	 MPI_Dims_create(6, 2, dims)   (3,2)
       (0,0)	 MPI_Dims_create(7, 2, dims)   (7,1)
       (0,3,0)	 MPI_Dims_create(6, 3, dims)   (2,3,1)
       (0,3,0)	 MPI_Dims_create(7, 3, dims)   erroneous call
       ------------------------------------------------------

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++ func-
       tions 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.

Open MPI 1.2							  September 2006					 MPI_Dims_create(3OpenMPI)