# MPI_Rget_accumulate_c

Perform an atomic, one-sided read-and-accumulate

## Synopsis

    #ifdef ENABLE_QMPI
    #ifndef MPICH_MPI_FROM_PMPI
    int QMPI_Rget_accumulate_c(QMPI_Context context, int tool_id, const void *origin_addr,
                               MPI_Count origin_count, MPI_Datatype origin_datatype, void *result_addr,
                               MPI_Count result_count, MPI_Datatype result_datatype, int target_rank,
                               MPI_Aint target_disp, MPI_Count target_count,
                               MPI_Datatype target_datatype, MPI_Op op, MPI_Win win,
                               MPI_Request *request) MPICH_API_PUBLIC

## Input Parameters

origin_addr
  initial address of buffer (choice) (choice)
origin_count
  number of entries in origin buffer (non-negative integer) (non-negative integer)
origin_datatype
  datatype of each entry in origin buffer (handle) (handle)
result_count
  number of entries in result buffer (non-negative integer) (non-negative integer)
result_datatype
  datatype of entries in result buffer (handle) (handle)
target_rank
  rank of target (non-negative integer) (non-negative integer)
target_disp
  displacement from start of window to beginning of target buffer (non-negative integer) (non-negative integer)
target_count
  number of entries in target buffer (non-negative integer) (non-negative integer)
target_datatype
  datatype of each entry in target buffer (handle) (handle)
op
  reduce operation (handle) (handle)
win
  window object (handle) (handle)

## Output Parameters

result_addr
  initial address of result buffer (choice) (choice)
request
  RMA request (handle) (handle)

## Notes

This operations is atomic with respect to other "accumulate" operations.

The get and accumulate steps are executed atomically for each basic element in the datatype (see MPI 3.0 Section 11.7 for details). The predefined operation `MPI_REPLACE` provides fetch-and-set behavior.

The basic components of both the origin and target datatype must be the same predefined datatype (e.g., all `MPI_INT` or all `MPI_DOUBLE_PRECISION`).

## Notes for Fortran

All MPI routines in Fortran (except for `MPI_WTIME` and `MPI_WTICK`) have an additional argument `ierr` at the end of the argument list. `ierr` is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the `call` statement.

All MPI objects (e.g., `MPI_Datatype`, `MPI_Comm`) are of type `INTEGER` in Fortran.

## Errors

All MPI routines (except `MPI_Wtime` and `MPI_Wtick`) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with `MPI_Comm_set_errhandler` (for communicators), `MPI_File_set_errhandler` (for files), and `MPI_Win_set_errhandler` (for RMA windows). The MPI-1 routine `MPI_Errhandler_set` may be used but its use is deprecated. 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; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS
  No error; MPI routine completed successfully.

MPI_ERR_ARG
  Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., `MPI_ERR_RANK`).

MPI_ERR_BUFFER
  Invalid buffer pointer. Usually a null buffer where one is not valid.

MPI_ERR_COUNT
  Invalid count argument. Count arguments must be non-negative; a count of zero is often valid.

MPI_ERR_DISP

MPI_ERR_RANK
  Invalid source or destination rank. Ranks must be between zero and the size of the communicator minus one; ranks in a receive (`MPI_Recv`, `MPI_Irecv`, `MPI_Sendrecv`, etc.) may also be `MPI_ANY_SOURCE`.

MPI_ERR_TYPE
  Invalid datatype argument. Additionally, this error can occur if an uncommitted MPI_Datatype (see `MPI_Type_commit`) is used in a communication call.

MPI_ERR_WIN
  Invalid MPI window object

MPI_ERR_OTHER
  Other error; use `MPI_Error_string` to get more information about this error code.

## See Also

MPI_Get_accumulate MPI_Fetch_and_op