NAME

       MPI_Comm_rank - Determines the rank of the calling process in the communicator.

SYNTAX

C Syntax

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

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_COMM_RANK(COMM, RANK, IERROR)
            INTEGER   COMM, RANK, IERROR

C++ Syntax

       #include <mpi.h>
       int Comm::Get_rank() const

INPUT PARAMETERS

       comm      Communicator (handle).

OUTPUT PARAMETERS

       rank      Rank of the calling process in group of comm (integer).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       This  function  gives the rank of the process in the particular communicator's group. It is equivalent to
       accessing the communicator's group with MPI_Comm_group, computing the rank using MPI_Group_rank, and then
       freeing the temporary group via MPI_Group_free.

       Many programs will be written with the master-slave model, where  one  process  (such  as  the  rank-zero
       process)  will  play  a  supervisory  role,  and the other processes will serve as compute nodes. In this
       framework, MPI_Comm_size and MPI_Comm_rank are useful for determining the roles of the various  processes
       of a communicator.

ERRORS

       Almost  all  MPI  routines  return  an  error  value; C routines as the value of the function and Fortran
       routines in the last argument. C++ functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS, then on error the  C++  exception  mechanism  will  be  used  to  throw  an
       MPI::Exception object.

       Before  the  error  value  is  returned,  the current MPI error handler is called. By default, this error
       handler aborts the MPI job, except for I/O function  errors.  The  error  handler  may  be  changed  with
       MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values
       to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

SEE ALSO

       MPI_Comm_group
       MPI_Comm_size
       MPI_Comm_compare

1.10.2                                            Jan 21, 2016                                  MPI_Comm_rank(3)