NAME

       MPI_Barrier, MPI_Ibarrier - Synchronization between MPI processes in a group

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Barrier(MPI_Comm comm)

       int MPI_Ibarrier(MPI_Comm comm, MPI_Request *request)

Fortran Syntax

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

       MPI_IBARRIER(COMM, REQUEST, IERROR)
            INTEGER   COMM, REQUEST, IERROR

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Barrier(comm, ierror)
            TYPE(MPI_Comm), INTENT(IN) :: comm
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

       MPI_Ibarrier(comm, request, ierror)
            TYPE(MPI_Comm), INTENT(IN) :: comm
            TYPE(MPI_Request), INTENT(OUT) :: request
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

       #include <mpi.h>
       void MPI::Comm::Barrier() const = 0

INPUT PARAMETER

       comm      Communicator (handle).

OUTPUT PARAMETERS

       request   Request (handle, non-blocking only).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       An MPI barrier completes after all group members have entered the barrier.

WHEN COMMUNICATOR IS AN INTER-COMMUNICATOR

       When  the communicator is an inter-communicator, the barrier operation is performed across
       all processes in both groups.  All processes in the first group may exit the barrier  when
       all processes in the second group have entered the barrier.

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_Bcast