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       MPI_Win_create -  Create an MPI Window object for one-sided communication


       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)
              - local unit size for displacements, in bytes (positive integer)
       info   - info argument (handle)
       comm   - communicator (handle)


       win    - window object returned by the call (handle)


       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.

              -  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

              -  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".

              -  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.


       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.


       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.


       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.

              - No error; MPI routine completed successfully.
              - Invalid argument.  Some argument is invalid and is not identified by  a  specific
              error class (e.g., MPI_ERR_RANK ).
              -  Invalid  communicator.   A  common error is to use a null communicator in a call
              (not even allowed in MPI_Comm_rank ).
              - Invalid Info
              - Other error; use MPI_Error_string to get more information about this error code.


       MPI_Win_allocate MPI_Win_allocate_shared MPI_Win_create_dynamic MPI_Win_free

                                            11/21/2018                          MPI_Win_create(3)