mpi_dims_create(3openmpi) [osx man page]

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)

Check Out this Related Man Page

MPI_Graphdims_get(3OpenMPI)											       MPI_Graphdims_get(3OpenMPI)

NAME

       MPI_Graphdims_get  - Retrieves graph topology information associated with a communicator.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Graphdims_get(MPI_Comm comm, int *nnodes, int *nedges)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_GRAPHDIMS_GET(COMM, NNODES, NEDGES, IERROR)
	    INTEGER   COMM, NNODES, NEDGES, IERROR

C++ Syntax
       #include <mpi.h>
       void Graphcomm::Get dims(int nnodes[], int nedges[]) const

INPUT PARAMETER

       comm	 Communicator for group with graph structure (handle).

OUTPUT PARAMETERS

       nnodes	 Number of nodes in graph (integer).

       nedges	 Number of edges in graph (integer).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       Functions  MPI_Graphdims_get  and  MPI_Graph_get  retrieve  the	graph-topology	information  that  was	associated  with a communicator by
       MPI_Graph_create.

       The information provided by MPI_Graphdims_get can be used to dimension the vectors index and edges correctly for a call to MPI_Graph_get.

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_create
       MPI_Graph_get

Open MPI 1.2							  September 2006				       MPI_Graphdims_get(3OpenMPI)

Linux and UNIX Man Pages

mpi_dims_create(3openmpi) [osx man page]

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