--- name: "MPI_Get_accumulate.openmpi" section: "3" platform: "linux" package: "openmpi-doc" version: "5.0.7-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/MPI_Get_accumulate.openmpi" --- # MPI\_Get\_accumulate.openmpi(3) *MPI\_Get\_accumulate*, *MPI\_Rget\_accumulate* - Combines the contents of the origin buffer with that of a target buffer and returns the target buffer value. ## SYNTAX ### C Syntax ``` #include int MPI_Get_accumulate(const void *origin_addr, int origin_count, MPI_Datatype origin_datatype, void *result_addr, int result_count, MPI_Datatype result_datatype, int target_rank, MPI_Aint target_disp, int target_count, MPI_Datatype target_datatype, MPI_Op op, MPI_Win win) int MPI_Rget_accumulate(const void *origin_addr, int origin_count, MPI_Datatype origin_datatype, void *result_addr, int result_count, MPI_Datatype result_datatype, int target_rank, MPI_Aint target_disp, int target_count, MPI_Datatype target_datatype, MPI_Op op, MPI_Win win, MPI_Request *request) ``` ### Fortran Syntax ``` USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_GET_ACCUMULATE(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, RESULT_ADDR, RESULT_COUNT, RESULT_DATATYPE, TARGET_RANK, TARGET_DISP, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, IERROR) ORIGIN_ADDR, RESULT_ADDR(*) INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_COUNT, TARGET_DATATYPE, TARGET_RANK, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, IERROR MPI_RGET_ACCUMULATE(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, RESULT_ADDR, RESULT_COUNT, RESULT_DATATYPE, TARGET_RANK, TARGET_DISP, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, REQUEST, IERROR) ORIGIN_ADDR, RESULT_ADDR(*) INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_COUNT, TARGET_DATATYPE, TARGET_RANK, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, REQUEST, IERROR ``` ### Fortran 2008 Syntax ``` USE mpi_f08 MPI_Get_accumulate(origin_addr, origin_count, origin_datatype, result_addr, result_count, result_datatype, target_rank, target_disp, target_count, target_datatype, op, win, ierror) TYPE(*), DIMENSION(..), INTENT(IN) :: origin_addr TYPE(*), DIMENSION(..) :: result_addr INTEGER, INTENT(IN) :: origin_count, result_count, target_rank, target_count TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype, result_datatype INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_dist TYPE(MPI_Op), INTENT(IN) :: op TYPE(MPI_Win), INTENT(IN) :: win INTEGER, OPTIONAL, INTENT(OUT) :: ierror MPI_Rget_accumulate(origin_addr, origin_count, origin_datatype, result_addr, result_count, result_datatype, target_rank, target_disp, target_count, target_datatype, op, win, request, ierror) TYPE(*), DIMENSION(..), INTENT(IN) :: origin_addr TYPE(*), DIMENSION(..) :: result_addr INTEGER, INTENT(IN) :: origin_count, result_count, target_rank, target_count TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype, result_datatype INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_dist TYPE(MPI_Op), INTENT(IN) :: op TYPE(MPI_Win), INTENT(IN) :: win TYPE(MPI_Request), INTENT(OUT) :: request INTEGER, OPTIONAL, INTENT(OUT) :: ierror ``` ## INPUT PARAMETERS - • **origin\_addr** : Initial address of buffer (choice). - • **origin\_count** : Number of entries in buffer (nonnegative integer). - • **origin\_datatype** : Data type of each buffer entry (handle). - • **result\_addr** : Initial address of result buffer (choice). - • - **result\_count (Number of entries in result buffer (nonnegative)** integer). - • **result\_datatype** : Data type of each result buffer entry (handle). - • **target\_rank** : Rank of target (nonnegative integer). - • - **target\_disp (Displacement from start of window to beginning of)** target buffer (nonnegative integer). - • - **target\_count (Number of entries in target buffer (nonnegative)** integer). - • **target\_datatype** : Data type of each entry in target buffer (handle). - • **op** : Reduce operation (handle). - • **win** : Window object (handle). ## OUTPUT PARAMETER - • *MPI\_Rget\_accumulate*: RMA request - • **ierror** : Fortran only: Error status (integer). ## DESCRIPTION *MPI\_Get\_accumulate* is a function used for one-sided MPI communication that adds the contents of the origin buffer (as defined by origin\_addr, origin\_count, and origin\_datatype) to the buffer specified by the arguments target\_count and target\_datatype, at offset target\_disp, in the target window specified by target\_rank and win, using the operation op. *MPI\_Get\_accumulate* returns in the result buffer result\_addr the contents of the target buffer before the accumulation. Any of the predefined operations for *MPI\_Reduce*, as well as MPI\_NO\_OP, can be used. User-defined functions cannot be used. For example, if op is MPI\_SUM, each element of the origin buffer is added to the corresponding element in the target, replacing the former value in the target. Each datatype argument must be a predefined data type or a derived data type, where all basic components are of the same predefined data type. Both datatype arguments must be constructed from the same predefined data type. The operation op applies to elements of that predefined type. The target\_datatype argument must not specify overlapping entries, and the target buffer must fit in the target window. A new predefined operation, MPI\_REPLACE, is defined. It corresponds to the associative function f(a, b) =b; that is, the current value in the target memory is replaced by the value supplied by the origin. A new predefined operation, MPI\_NO\_OP, is defined. It corresponds to the assiciative function f(a, b) = a; that is the current value in the target memory is returned in the result buffer at the origin and no operation is performed on the target buffer. *MPI\_Rget\_accumulate* is similar to *MPI\_Get\_accumulate*, except that it allocates a communication request object and associates it with the request handle (the argument request) that can be used to wait or test for completion. The completion of an *MPI\_Rget\_accumulate* operation indicates that the data is available in the result buffer and the origin buffer is free to be updated. It does not indicate that the operation has been completed at the target window. ## NOTES The generic functionality of *MPI\_Get\_accumulate* might limit the performance of fetch-and-increment or fetch-and-add calls that might be supported by special hardware operations. *MPI\_Fetch\_and\_op* thus allows for a fast implementation of a commonly used subset of the functionality of *MPI\_Get\_accumulate*. *MPI\_Get* is a special case of *MPI\_Get\_accumulate*, with the operation MPI\_NO\_OP. Note, however, that *MPI\_Get* and *MPI\_Get\_accumulate* have different constraints on concurrent updates. It is the user’s responsibility to guarantee that, when using the accumulate functions, the target displacement argument is such that accesses to the window are properly aligned according to the data type arguments in the call to the *MPI\_Get\_accumulate* function. ## ERRORS Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument. Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI\_COMM\_SELF and will call the associated MPI error handler. When MPI\_COMM\_SELF is not initialized (i.e., before *MPI\_Init*/*MPI\_Init\_thread*, after *MPI\_Finalize*, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling *MPI\_Comm\_set\_errhandler* on MPI\_COMM\_SELF when using the World model, or the mpi\_initial\_errhandler CLI argument to mpiexec or info key to *MPI\_Comm\_spawn*/*MPI\_Comm\_spawn\_multiple*. If no other appropriate error handler has been set, then the MPI\_ERRORS\_RETURN error handler is called for MPI I/O functions and the MPI\_ERRORS\_ABORT error handler is called for all other MPI functions. Open MPI includes three predefined error handlers that can be used: - • **MPI\_ERRORS\_ARE\_FATAL** Causes the program to abort all connected MPI processes. - • **MPI\_ERRORS\_ABORT** An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if *MPI\_Abort* was called on that communicator. If called on a window or file, acts as if *MPI\_Abort* was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process. - • **MPI\_ERRORS\_RETURN** Returns an error code to the application. MPI applications can also implement their own error handlers by calling: - • *MPI\_Comm\_create\_errhandler* then *MPI\_Comm\_set\_errhandler* - • *MPI\_File\_create\_errhandler* then *MPI\_File\_set\_errhandler* - • *MPI\_Session\_create\_errhandler* then *MPI\_Session\_set\_errhandler* or at *MPI\_Session\_init* - • *MPI\_Win\_create\_errhandler* then *MPI\_Win\_set\_errhandler* Note that MPI does not guarantee that an MPI program can continue past an error. See the *MPI man page* for a full list of *MPI error codes*. See the Error Handling section of the MPI-3.1 standard for more information. **SEE ALSO:** *MPI\_Put* *MPI\_Reduce* ## COPYRIGHT 2003-2025, The Open MPI Community