---
name: "MPI_Get_accumulate_c"
section: "3"
platform: "linux"
package: "mpich-doc"
version: "4.0.2-3"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_Get_accumulate_c"
---

# MPI\_Get\_accumulate\_c(3)

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

## NAME

MPI\_Get\_accumulate\_c -  Perform an atomic, one-sided read-and-accumulate operation

## SYNOPSIS

```
int MPI_Get_accumulate_c(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)
```

## 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 each entry 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)

## 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 origin and result buffers (origin\_addr and result\_addr) must be disjoint. Each datatype argument must be a predefined datatype or a derived datatype where all basic components are of the same predefined datatype. All datatype arguments must be constructed from the same predefined datatype. The operation op applies to elements of that predefined type. target\_datatype must not specify overlapping entries, and the target buffer must fit in the target window or in attached memory in a dynamic window.

Any of the predefined operations for  *MPI\_Reduce* , as well as  *MPI\_NO\_OP* or *MPI\_REPLACE* can be specified as op. User-defined functions cannot be used. A new predefined operation,  *MPI\_NO\_OP* , is defined. It corresponds to the associative function f (a, b) = a; i.e., 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\_NO\_OP* can be used only in  *MPI\_Get\_accumulate* , *MPI\_Rget\_accumulate* , and  *MPI\_Fetch\_and\_op* . *MPI\_NO\_OP* cannot be used in *MPI\_Accumulate* ,  *MPI\_Raccumulate* , or collective reduction operations, such as *MPI\_Reduce* and others.

## 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\_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\_Rget\_accumulate MPI\_Fetch\_and\_op\