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

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

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