MPI_Barrier(3)                     Open MPI                     MPI_Barrier(3)



NAME
       MPI_Barrier - Blocks until all processes have reached this routine.


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


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_BARRIER(COMM, IERROR)
            INTEGER   COMM, IERROR


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


INPUT PARAMETER
       comm      Communicator (handle).


OUTPUT PARAMETER
       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       Blocks the caller until all group members have called it; the call
       returns at any process only after all group members have entered the
       call.


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



1.4.1                            Jan 14, 2010                   MPI_Barrier(3)
