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.

MPI_DIMS_CREATE(nnodes, ndims, dims) | |

IN nnodes | number of nodes in a grid (integer) |

IN ndims | number of cartesian dimensions (integer) |

INOUT dims | integer array of size ndims specifying the number of nodes in each dimension |

` int MPI_Dims_create(int nnodes, int ndims, int *dims) `

` MPI_DIMS_CREATE(NNODES, NDIMS, DIMS, IERROR) INTEGER NNODES, NDIMS, DIMS(*), IERROR `

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
.

For ` dims[i]` set by the call, ` dims[i]` will be ordered in
non-increasing order. Array ` dims` is suitable for use as input to
routine MPI_CART_CREATE. MPI_DIMS_CREATE is local.

** Example**

dims | function call | dims |

before 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 |

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