DragonFly On-Line Manual Pages
MPI_Win_lock(3) MPI MPI_Win_lock(3)
MPI_Win_lock - Begin an RMA access epoch at the target process.
int MPI_Win_lock(int lock_type, int rank, int assert, MPI_Win win)
- Indicates whether other processes may access the target window
at the same time (if MPI_LOCK_SHARED ) or not (
rank - rank of locked window (nonnegative integer)
assert - Used to optimize this call; zero may be used as a default.
See notes. (integer)
win - window object (handle)
The name of this routine is misleading. In particular, this routine
need not block, except when the target process is the calling process.
Implementations may restrict the use of RMA communication that is
synchronized by lock calls to windows in memory allocated by
MPI_Alloc_mem . Locks can be used portably only in such memory.
The assert argument is used to indicate special conditions for the
fence that an implementation may use to optimize the MPI_Win_lock
operation. The value zero is always correct. Other assertion values
may be or'ed together. Assertions that are valid for MPI_Win_lock are:
- no other process holds, or will attempt to acquire a
conflicting lock, while the caller holds the window lock. This
is useful when mutual exclusion is achieved by other means, but
the coherence operations that may be attached to the lock and
unlock calls are still required.
THREAD AND INTERRUPT SAFETY
This routine is thread-safe. This means that this routine may be
safely used by multiple threads without the need for any user-provided
thread locks. However, the routine is not interrupt safe. Typically,
this is due to the use of memory allocation routines such as malloc or
other non-MPICH runtime routines that are themselves not interrupt-
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 call statement.
All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
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_Comm_set_errhandler (for
communicators), MPI_File_set_errhandler (for files), and
MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine
MPI_Errhandler_set may be used but its use is deprecated. 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 an error; however, MPI implementations will
attempt to continue whenever possible.
- No error; MPI routine completed successfully.
- Invalid source or destination rank. Ranks must be between
zero and the size of the communicator minus one; ranks in a
receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also
be MPI_ANY_SOURCE .
- Invalid MPI window object
- Other error; use MPI_Error_string to get more information
about this error code.