MPI_Win_create(3)                  Open MPI                  MPI_Win_create(3)



NAME
       MPI_Win_create - One-sided MPI call that returns a window object for
       RMA operations.


SYNTAX
C Syntax
       #include <mpi.h>
       MPI_Win_create(void *base, MPI_Aint size, int disp_unit,
            MPI_Info info, MPI_Comm comm, MPI_Win *win)


Fortran Syntax (see FORTRAN 77 NOTES)
       INCLUDE 'mpif.h'
       MPI_WIN_CREATE(BASE, SIZE, DISP_UNIT, INFO, COMM, WIN, IERROR)
            <type> BASE(*)
            INTEGER(KIND=MPI_ADDRESS_KIND) SIZE
            INTEGER DISP_UNIT, INFO, COMM, WIN, IERROR


C++ Syntax
       #include <mpi.h>
       static MPI::Win MPI::Win::Create(const void* base,
            MPI::Aint size, int disp_unit, const
            MPI::Info& info, const MPI::Intracomm& comm)


INPUT PARAMETERS
       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).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_Win_create is a one-sided MPI communication 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. A process may elect to expose
       no memory by specifying size = 0.

       If the base value used by MPI_Win_create was allocated by
       MPI_Alloc_mem, the size of the window can be no larger than the value
       set by the MPI_ALLOC_MEM function.

       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 following info key is supported:

       no_locks  If MPI_Win_lock is called on a window created with this info
                 key, the call will fail. If this info key is present, it is
                 assumed that the local window is never locked, allowing
                 several internal checks to be skipped, permitting a more
                 efficient implementation.



NOTES
       Common choices for disp_unit are 1 (no scaling), and (in C syntax)
       sizeof(type), for a window that consists of an array of elements of
       type type. The later choice will allow one to use array indices in RMA
       calls, and have those scaled correctly to byte displacements, even in a
       heterogeneous environment.

       Use memory allocated by MPI_Alloc_mem to guarantee properly aligned
       window boundaries (such as word, double-word, cache line, page frame,
       and so on).





FORTRAN 77 NOTES
       The MPI standard prescribes portable Fortran syntax for the SIZE
       argument only for Fortran 90. FORTRAN 77 users may use the non-portable
       syntax

            INTEGER*MPI_ADDRESS_KIND SIZE

       where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the
       length of the declared integer in bytes.


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.






1.4.1                            Jan 14, 2010                MPI_Win_create(3)
