NAME¶
MPI_Win_create - Create an MPI Window object for one-sided communication
SYNOPSIS¶
int MPI_Win_create(void *base, MPI_Aint size, int disp_unit, MPI_Info info,
MPI_Comm comm, MPI_Win *win)
This is a collective call executed by all processes in the group of comm. It
returns a window object that can be used by these processes to perform RMA
operations. Each process specifies a window of existing memory that it exposes
to RMA accesses by the processes in the group of comm. The window consists of
size bytes, starting at address base. In C, base is the starting address of a
memory region. In Fortran, one can pass the first element of a memory region
or a whole array, which must be 'simply contiguous' (for 'simply contiguous',
see also MPI 3.0, Section 17.1.12 on page 626). A process may elect to expose
no memory by specifying size = 0.
- base
- - initial address of window (choice)
- size
- - size of window in bytes (nonnegative integer)
- disp_unit
- - local unit size for displacements, in bytes (positive integer)
- info
- - info argument (handle)
- comm
- - communicator (handle)
OUTPUT PARAMETERS¶
- win
- - window object returned by the call (handle)
NOTES¶
The displacement unit argument is provided to facilitate address arithmetic in
RMA operations: the target displacement argument of an RMA operation is scaled
by the factor disp_unit specified by the target process, at window creation.
The info argument provides optimization hints to the runtime about the expected
usage pattern of the window. The following info keys are predefined.
- no_locks
- - If set to true, then the implementation may assume that passive target
synchronization (i.e., MPI_Win_lock , MPI_Win_lock_all )
will not be used on the given window. This implies that this window is not
used for 3-party communication, and RMA can be implemented with no (less)
asynchronous agent activity at this process.
- accumulate_ordering
- - Controls the ordering of accumulate operations at the target. The
argument string should contain a comma-separated list of the following
read/write ordering rules, where e.g. "raw" means
read-after-write: "rar,raw,war,waw".
- accumulate_ops
- - If set to same_op, the implementation will assume that all concurrent
accumulate calls to the same target address will use the same operation.
If set to same_op_no_op, then the implementation will assume that all
concurrent accumulate calls to the same target address will use the same
operation or MPI_NO_OP . This can eliminate the need to protect
access for certain operation types where the hardware can guarantee
atomicity. The default is same_op_no_op.
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
call statement.
All MPI objects (e.g.,
MPI_Datatype ,
MPI_Comm ) are of type
INTEGER in Fortran.
ERRORS¶
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.
- MPI_SUCCESS
- - No error; MPI routine completed successfully.
- MPI_ERR_ARG
- - Invalid argument. Some argument is invalid and is not identified by a
specific error class (e.g., MPI_ERR_RANK ).
- MPI_ERR_COMM
- - Invalid communicator. A common error is to use a null communicator in a
call (not even allowed in MPI_Comm_rank ).
- MPI_ERR_INFO
- - Invalid Info
- MPI_ERR_OTHER
- - Other error; use MPI_Error_string to get more information about
this error code.
- MPI_ERR_SIZE
- -
SEE ALSO¶
MPI_Win_allocate MPI_Win_allocate_shared MPI_Win_create_dynamic MPI_Win_free
LOCATION¶
/tmp/gyCYfBi4J6/mpich-3.1/src/mpi/rma/win_create.c