MPI_Win_create(3OpenMPI) MPI_Win_create(3OpenMPI)
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 opera-tions. operations.
tions. Each process specifies a window of existing memory that it exposes to RMA accesses by the pro-cesses processes
cesses 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 environ-ment. environment.
ment.
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. FOR-TRAN FORTRAN
TRAN 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.
Open MPI 1.2 March 2007 MPI_Win_create(3OpenMPI)
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