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)
USE MPI
! or the older form: 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
Fortran 2008 Syntax
USE mpi_f08
MPI_Win_create(base, size, disp_unit, info, comm, win, ierror)
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: base
INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: size
INTEGER, INTENT(IN) :: disp_unit
TYPE(MPI_Info), INTENT(IN) :: info
TYPE(MPI_Comm), INTENT(IN) :: comm
TYPE(MPI_Win), INTENT(OUT) :: win
INTEGER, OPTIONAL, INTENT(OUT) :: 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 inte-
ger).
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 exe-
cuted 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_Al-
loc_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 arith-
metic in RMA operations: the target displacement argument of an RMA op-
eration is scaled by the factor disp_unit specified by the target
process, at window creation.
The following info keys are supported:
no_locks If set to true, then the implementation may assume that the
local window is never locked (by a call to MPI_Win_lock or
MPI_Win_lock_all). Setting this value if only active syn-
chronization may allow the implementation to enable certain
optimizations.
accumulate_ordering
By default, accumulate operations from one initiator to one
target on the same window are strictly ordered. If the info
key accumulate_ordering is set to none, no ordering of accu-
mulate operations guaranteed. They key can also be a comma-
separated list of required orderings consisting of rar, war,
raw, and waw for read-after-read, write-after-read, read-af-
ter-write, and write-after-write, respectively. Looser or-
dering constraints are likely to result in improved perfor-
mance.
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. The default is same_op_no_op.
same_size If set to true, then the implementation may assume that the
argument size is identical on all processes, and that all
processes have provided this info key with the same value.
same_disp_unit
If set to true, then the implementation may assume that the
argument disp_unit is identical on all processes, and that
all processes have provided this info key with the same
value.
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 argu-
ment 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++ func-
tions 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.
SEE ALSO
MPI_Alloc_mem MPI_Free_mem MPI_Win_allocate MPI_Win_allocate_shared
4.1.2 Nov 24, 2021 MPI_Win_create(3)
Generated by dwww version 1.14 on Sun Apr 20 08:17:17 CEST 2025.