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.