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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_Cart_map(3) 							MPI							   MPI_Cart_map(3)

NAME

       MPI_Cart_map -  Maps process to Cartesian topology information

SYNOPSIS

       int MPI_Cart_map(MPI_Comm comm_old, int ndims, int *dims, int *periods,
		       int *newrank)

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 PARAMETER

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

THREAD AND INTERRUPT SAFETY

       This  routine  is  both	thread- and interrupt-safe.  This means that this routine may safely be used by multiple threads and from within a
       signal handler.

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the end of the argument  list.   ierr
       is  an integer and has the same meaning as the return value of the routine in C.  In Fortran, MPI routines are subroutines, and are invoked
       with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of the function and Fortran  routines	in
       the  last  argument.  Before the value is returned, the current MPI error handler is called.  By default, this error handler aborts the MPI
       job.  The error handler may  be	changed  with  MPI_Comm_set_errhandler	(for  communicators),  MPI_File_set_errhandler	(for  files),  and
       MPI_Win_set_errhandler  (for  RMA  windows).   The  MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated.  The predefined
       error handler MPI_ERRORS_RETURN may be used to cause error values to be returned.  Note that MPI does not guarentee that an MPI program can
       continue past an error; however, MPI implementations will attempt to continue whenever possible.

       MPI_SUCCESS
	      - No error; MPI routine completed successfully.
       MPI_ERR_COMM
	      - Invalid communicator.  A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank ).
       MPI_ERR_DIMS
	      - Invalid dimension argument.  A dimension argument is null or its length is less than or equal to zero.
       MPI_ERR_ARG
	      - Invalid argument.  Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK ).

LOCATION

       cart_map.c

								     7/27/2010							   MPI_Cart_map(3)
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