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NAME

MPI_Dims_create - Creates a suitable set of cartesian dimensions

SYNOPSIS

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

#include <pmpi.h> int PMPI_Dims_create(int nnodes , int ndims , int *dims );

#include <mpi.h> void MPI::Compute_dims(int nnodes , int ndims , int *dims );

INCLUDE 'mpif.h' MPI_DIMS_CREATE(nnodes , ndims , dims , ierr ) INTEGER nnodes , ndims , dims , ierr

INPUT PARAMETERS

nnodes - Total number of elements in the cartesian array (integer)

ndims - number of dimensions (integer)

dims - fixed dimensions (array)

OUTPUT PARAMETER

dims - dimensions that multiply to give the total number of nodes (array).

DESCRIPTION

The MPI_Dims_create() function is used to determine a set of dimensions that may be used for the MPI_Cart_create() function. It will produce a set of ndims integers that multiply to give nnodes .

The dims array is used for both input and output. Any zero entries are filled with integers to make the new dimensions as close to each other as possible. If an entry is non-zero, then it will be used instead. If such an entry is either negative, or not an exact divisor of nnodes then it is an error, and MPI_ERR_DIMS will be returned. Any new dimensions are added in order of size.

PMPI_Dims_create() is the profiling version of this function.

ERRORS

All MPI routines except for MPI_Wtime and MPI_Wtick return an error code. The the current MPI error handler is invoked if the return value is not MPI_SUCCESS. The default error handler aborts, but this may be changed with by using the MPI_Errhandler_set() function. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. Note that MPI does not guarentee that an MPI program can continue past an error. In this implementation, all errors except MPI_ERR_INTERN or MPI_ERR_OTHER should always be recoverable.

In C, the error code is passed as the return value. In FORTRAN, all functions have an parameter ierr which returns the error code. MPI C++ functions do not directly return an error code. However, C++ users may want to use the MPI::ERRORS_THROW_EXCEPTIONS handler. This will throw an MPI::Exception with the corresponding error code. To prevent exceptions from being raised from within C and Fortran code, they will see all error return values as MPI_ERR_PENDING when this handler is chosen. In this implementation, call MPI::throw_exception() to throw the correct exception if this occurs.

MPI_SUCCESS - No error;

MPI_ERR_PENDING - Pending exception;

MPI_ERR_DIMS - Invalid dimensions;

MPI_ERR_ARG - Invalid input or output pointer.

SEE ALSO

MPI_Cart_create (3) MPI_Cartdim_get (3) MPI_Cart_get (3) MPI_Graph_create (3) MPI_Graphdims_get (3)

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