trusty (3) MPI_Win_create.openmpi.3.gz

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.