MPI_DIMS_CREATE, MPI_Dims_create

Purpose

Defines a cartesian grid to balance tasks.

C synopsis

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

C++ synopsis

#include mpi.h
void MPI::Compute_dims(int nnodes, int ndims, int dims[]);

FORTRAN synopsis

include 'mpif.h' or use mpi
MPI_DIMS_CREATE(INTEGER NNODES,INTEGER NDIMS,INTEGER DIMS(*),
      INTEGER IERROR)

Parameters

nnodes
     is an integer specifying the number of nodes in a grid (IN)

ndims
     is an integer specifying the number of cartesian dimensions (IN)

dims
     is an integer array of size ndims that specifies the number of nodes
     in each dimension. (INOUT)

IERROR
     is the FORTRAN return code. It is always the last argument.

Description

This subroutine creates a cartesian grid with a given number of dimensions
and a given number of nodes. The dimensions are constrained to be as close
to each other as possible.

If dims[i] is a positive number when MPI_DIMS_CREATE is called, the routine
will not modify the number of nodes in dimension i. Only those entries
where dims[i]=0 are modified by the call.

Notes

MPI_DIMS_CREATE chooses dimensions so that the resulting grid is as close
as possible to being an ndims-dimensional cube.

Errors

MPI not initialized

MPI already finalized

Invalid ndims
     ndims < 0

Invalid nnodes
     nnodes < 0

Invalid dimension
     dims[i] < 0 or nnodes is not a multiple of the non-zero entries of
     dims

Related information

     MPI_CART_CREATE