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