MPI Subroutine Reference

MPI_CART_MAP, MPI_Cart_map

Purpose

Computes placement of tasks on the physical processor.

C synopsis

#include <mpi.h>
MPI_Cart_map(MPI_Comm comm,int ndims,int *dims,int *periods,
	     int *newrank);

C++ synopsis

#include mpi.h
int MPI::Cartcomm::Map(int ndims, const int dims[], 
		       const bool periods[]) const;

FORTRAN synopsis

include 'mpif.h' or use mpi
MPI_CART_MAP(INTEGER COMM,INTEGER NDIMS,INTEGER DIMS(*),
	     INTEGER PERIODS(*),INTEGER NEWRANK,INTEGER IERROR)

Parameters

comm

is the input communicator (handle) (IN)

ndims

is the number of dimensions of the cartesian structure (integer) (IN)

dims

is an integer array of size ndims specifying the number of tasks in each coordinate direction (IN)

periods

is a logical array of size ndims specifying the periodicity in each coordinate direction (IN)

newrank

is the reordered rank or MPI_UNDEFINED if the calling task does not belong to the grid (integer) (OUT)

IERROR

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

Description

MPI_CART_MAP allows MPI to compute an optimal placement for the calling task on the physical processor by reordering the tasks in comm.

Notes

The rank determined by MPI_CART_MAP depends on the distribution of task per node. The value may or may not match rank in MPI_COMM_WORLD.

Errors

MPI not initialized

MPI already finalized

Invalid communicator

Invalid communicator type

must be intracommunicator

Invalid ndims

ndims < 1 or ndims > groupsize

Invalid dimension

ndims[i] <= 0

Invalid grid size

n< 0 or n > groupsize, where n is the product of dims[i]