oracular (3) MPI_Comm_rank.openmpi.3.gz

Provided by: openmpi-doc_4.1.6-13.3ubuntu2_all bug

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
       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_COMM_RANK(COMM, RANK, IERROR)
            INTEGER   COMM, RANK, IERROR


Fortran 2008 Syntax
       USE mpi_f08
       MPI_Comm_rank(comm, rank, ierror)
            TYPE(MPI_Comm), INTENT(IN) :: comm
            INTEGER, INTENT(OUT) :: rank
            INTEGER, OPTIONAL, INTENT(OUT) :: 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 manager-worker 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