Start an RMA access epoch for MPI
int MPI_Win_start(MPI_Group group, int assert, MPI_Win win)
- group of target processes (handle)
- program assertion (integer)
- window object (handle)
The assert argument is used to indicate special conditions for the
fence that an implementation may use to optimize the MPI_Win_start
operation. The value zero is always correct. Other assertion values
may be or'ed together. Assertions that are valid for MPI_Win_start are:
- the matching calls to MPI_WIN_POST have already
completed on all target processes when the call to MPI_WIN_START is made.
The nocheck option can be specified in a start call if and only if it is
specified in each matching post call. This is similar to the optimization
of ready-send that may save a handshake when the handshake is implicit in
the code. (However, ready-send is matched by a regular receive, whereas
both start and post must specify the nocheck option.)
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-safe.
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_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 guarantee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
- No error; MPI routine completed successfully.
- Null or invalid group passed to function.
- Invalid MPI window object
- Other error; use MPI_Error_string to get more information
about this error code.