MPI_COMM_RANK, MPI_Comm_rank

Purpose

Returns the rank of the local task in the group associated with a communicator.

C synopsis

#include <mpi.h>
int MPI_Comm_rank(MPI_Comm comm,int *rank);

C++ synopsis

#include mpi.h
int MPI::Comm::Get_rank() const;

FORTRAN synopsis

include 'mpif.h' or use mpi
MPI_COMM_RANK(INTEGER COMM,INTEGER RANK,INTEGER IERROR)

Parameters

comm
     is the communicator (handle) (IN)

rank
     is an integer specifying the rank of the calling task in group of comm
     (OUT)

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

Description

This subroutine returns the rank of the local task in the group associated
with a communicator.

You can use this subroutine with MPI_COMM_SIZE to determine the amount of
concurrency available for a specific job. MPI_COMM_RANK indicates the rank
of the task that calls it in the range from 0...size - 1, where size is the
return value of MPI_COMM_SIZE.

This subroutine is a shortcut to accessing the communicator's group with
MPI_COMM_GROUP, computing the rank using MPI_GROUP_RANK and freeing the
temporary group by using MPI_GROUP_FREE.

If comm is an intercommunicator, rank is the rank of the local task in the
local group.

Errors

Invalid communicator

MPI not initialized

MPI already finalized

Related information

     MPI_GROUP_RANK