13.3.1. Put

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The execution of a put operation is similar to the execution of a send by the origin process and a matching receive by the target process. The obvious difference is that all arguments are provided by one call---the call executed by the origin process.

MPI_PUT(origin_addr, origin_count, origin_datatype, target_rank, target_disp, target_count, target_datatype, win)
IN origin_addrinitial address of origin buffer (choice)
IN origin_countnumber of entries in origin buffer (non-negative integer)
IN origin_datatypedatatype of each entry in origin buffer (handle)
IN target_rankrank of target (non-negative integer)
IN target_dispdisplacement from start of window to target buffer (non-negative integer)
IN target_countnumber of entries in target buffer (non-negative integer)
IN target_datatypedatatype of each entry in target buffer (handle)
IN winwindow used for communication (handle)
C binding
int MPI_Put(const void *origin_addr, int origin_count, MPI_Datatype origin_datatype, int target_rank, MPI_Aint target_disp, int target_count, MPI_Datatype target_datatype, MPI_Win win)
int MPI_Put_c(const void *origin_addr, MPI_Count origin_count, MPI_Datatype origin_datatype, int target_rank, MPI_Aint target_disp, MPI_Count target_count, MPI_Datatype target_datatype, MPI_Win win)
Fortran 2008 binding
MPI_Put(origin_addr, origin_count, origin_datatype, target_rank, target_disp, target_count, target_datatype, win, ierror)

TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: origin_addr
INTEGER, INTENT(IN) :: origin_count, target_rank, target_count
TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype
INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
TYPE(MPI_Win), INTENT(IN) :: win
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_Put(origin_addr, origin_count, origin_datatype, target_rank, target_disp, target_count, target_datatype, win, ierror) !(_c)

TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: origin_addr
INTEGER(KIND=MPI_COUNT_KIND), INTENT(IN) :: origin_count, target_count
TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype
INTEGER, INTENT(IN) :: target_rank
INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
TYPE(MPI_Win), INTENT(IN) :: win
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
Fortran binding
MPI_PUT(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK, TARGET_DISP, TARGET_COUNT, TARGET_DATATYPE, WIN, IERROR)

<type> ORIGIN_ADDR(*)
INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK, TARGET_COUNT, TARGET_DATATYPE, WIN, IERROR
INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP

Transfers origin_count successive entries of the type specified by the origin_datatype, starting at address origin_addr on the origin process, to the target process specified by the win, target_rank pair. The data are written in the target buffer at address mpiargtarget_addr = mpiargwindow_base + mpiargtarget_disp×mpiargdisp_unit, where window_base and disp_unit are the base address and window displacement unit specified at window initialization, by the target process.

The target buffer is specified by the arguments target_count and target_datatype.

The data transfer is the same as that which would occur if the origin process executed a send operation with arguments origin_addr, origin_count, origin_datatype, target_rank, tag, comm, and the target process executed a receive operation with arguments target_addr, target_count, target_datatype, source, tag, comm, where target_addr is the target buffer address computed as explained above, the values of tag are arbitrary valid matching tag values, and comm is a communicator for the group of win.

The communication must satisfy the same constraints as for a similar message-passing communication. The target_datatype may not specify overlapping entries in the target buffer. The message sent must fit, without truncation, in the target buffer. Furthermore, the target buffer must fit in the target window or in attached memory in a dynamic window.

The target_datatype argument is a handle to a datatype object defined at the origin process. However, this object is interpreted at the target process: the outcome is as if the target datatype object was defined at the target process by the same sequence of calls used to define it at the origin process. The target datatype must contain only relative displacements, not absolute addresses. The same holds for get and accumulate operations.


Advice to users.

The target_datatype argument is a handle to a datatype object that is defined at the origin process, even though it defines a data layout in the target process memory. This causes no problems in a homogeneous environment, or in a heterogeneous environment if only portable datatypes are used (portable datatypes are defined in Section Semantic Terms).

The performance of a put transfer can be significantly affected, on some systems, by the choice of window location and the shape and location of the origin and target buffer: transfers to a target window in memory allocated by MPI_ALLOC_MEM or MPI_WIN_ALLOCATE may be much faster on shared memory systems; transfers from contiguous buffers will be faster on most, if not all, systems; the alignment of the communication buffers may also impact performance. ( End of advice to users.)

Advice to implementors.

A high-quality implementation will attempt to prevent remote accesses to memory outside the window that was exposed by the MPI process. This is important both for debugging purposes and for protection with client-server codes that use RMA. That is, a high-quality implementation will check, if possible, window bounds on each RMA call, and raise an error at the origin call if an out-of-bound situation occurs. Note that the condition can be checked at the origin. Of course, the added safety achieved by such checks has to be weighed against the added cost of such checks. ( End of advice to implementors.)


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