Blocks until all process have reached this routine.
int MPI_Barrier ( comm )
- comm - communicator (handle)
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.
If the underlying device cannot do better, a tree-like or combine
algorithm is used to broadcast a message wto all members of the
communicator. We can modifiy this to use "blocks" at a later time
Notes for Fortran
All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have
an additional argument ierr at the end of the argument list. ierr
is an integer and has the same meaning as the return value of the routine
in C. In Fortran, MPI routines are subroutines, and are invoked with the
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER
All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value;
C routines as the value of the function and Fortran routines in the last
argument. Before the value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job. The error handler
may be changed with MPI_Errhandler_set; the predefined error handler
MPI_ERRORS_RETURN may be used to cause error values to be returned.
Note that MPI does not guarentee that an MPI program can continue past
- MPI_SUCCESS - No error; MPI routine completed successfully.
- MPI_ERR_COMM - Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in MPI_Comm_rank).