MPI_Win_create(3) Open MPI MPI_Win_create(3)NAMEMPI_Win_create - One-sided MPI call that returns a window object for
RMA operations.
SYNTAXC 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 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).
DESCRIPTIONMPI_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_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 arith‐
metic 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 sev‐
eral internal checks to be skipped, permitting a more effi‐
cient 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 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.
1.7.4 Feb 04, 2014 MPI_Win_create(3)
