| MPI_WIN_ALLOCATE(size, disp_unit, info, comm, baseptr, win) | |
| IN size | size of window in bytes (non-negative integer) |
| IN disp_unit | local unit size for displacements, in bytes (positive integer) |
| IN info | info argument (handle) |
| IN comm | intra-communicator (handle) |
| OUT baseptr | initial address of window (choice) |
| OUT win | window object returned by the call (handle) |
int MPI_Win_allocate(MPI_Aint size, int disp_unit, MPI_Info info, MPI_Comm comm, void *baseptr, MPI_Win *win)
MPI_Win_allocate(size, disp_unit, info, comm, baseptr, win, ierror)
USE, INTRINSIC :: ISO_C_BINDING, ONLY : C_PTR
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(C_PTR), INTENT(OUT) :: baseptr
TYPE(MPI_Win), INTENT(OUT) :: win
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_WIN_ALLOCATE(SIZE, DISP_UNIT, INFO, COMM, BASEPTR, WIN, IERROR)
INTEGER DISP_UNIT, INFO, COMM, WIN, IERROR
INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR
This is a collective call executed by all processes in the group of comm. On each process, it allocates memory of at least size bytes, returns a pointer to it, and returns a window object that can be used by all processes in comm to perform RMA operations. The returned memory consists of size bytes local to each process, starting at address baseptr and is associated with the window as if the user called MPI_WIN_CREATE on existing memory. The size argument may be different at each process and size = 0 is valid; however, a library might allocate and expose more memory in order to create a fast, globally symmetric allocation. The discussion of and rationales for MPI_ALLOC_MEM and MPI_FREE_MEM in Section Memory Allocation also apply to MPI_WIN_ALLOCATE; in particular, see the rationale in Section Memory Allocation for an explanation of the type used for baseptr.
If the Fortran compiler provides TYPE(C_PTR), then the following generic interface must be provided in the mpi module and should be provided in mpif.h through overloading, i.e., with the same routine name as the routine with INTEGER(KIND=MPI_ADDRESS_KIND) BASEPTR, but with a different specific procedure name:
INTERFACE MPI_WIN_ALLOCATE
SUBROUTINE MPI_WIN_ALLOCATE(SIZE, DISP_UNIT, INFO, COMM, BASEPTR, &
WIN, IERROR)
IMPORT :: MPI_ADDRESS_KIND
INTEGER DISP_UNIT, INFO, COMM, WIN, IERROR
INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR
END SUBROUTINE
SUBROUTINE MPI_WIN_ALLOCATE_CPTR(SIZE, DISP_UNIT, INFO, COMM, BASEPTR, &
WIN, IERROR)
USE, INTRINSIC :: ISO_C_BINDING, ONLY : C_PTR
IMPORT :: MPI_ADDRESS_KIND
INTEGER :: DISP_UNIT, INFO, COMM, WIN, IERROR
INTEGER(KIND=MPI_ADDRESS_KIND) :: SIZE
TYPE(C_PTR) :: BASEPTR
END SUBROUTINE
END INTERFACE
The base procedure name of this overloaded function is
MPI_WIN_ALLOCATE_CPTR. The implied specific procedure
names
are described in Section Interface Specifications, Procedure Names, and the Profiling Interface
.
Rationale.
By allocating (potentially aligned) memory instead of allowing the user
to pass in an arbitrary buffer, this call can improve the performance
for systems with remote direct memory access.
This also permits the collective allocation of memory and
supports what is sometimes called the ``symmetric allocation'' model
that can be more scalable (for example, the implementation can
arrange to return an address for the allocated memory that is the
same on all processes).
( End of rationale.)
The info argument can be used to specify hints
similar to the info argument for MPI_WIN_CREATE and
MPI_ALLOC_MEM.