MPI_Comm_rank(3) Open MPI MPI_Comm_rank(3)
NAME
MPI_Comm_rank - Determines the rank of the calling process in the com-
municator.
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 communi-
cator'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++ func-
tions 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
4.1.2 Nov 24, 2021 MPI_Comm_rank(3)
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