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.