NAME

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

SYNOPSIS

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)

Accumulate origin_count elements of type origin_datatype from the origin buffer (origin_addr) to the buffer at offset target_disp, in the target window specified by target_rank and win, using the operation op and return in the result buffer result_addr the content of the target buffer before the accumulation.

INPUT PARAMETERS

origin_addr: - initial address of buffer (choice)
origin_count: - number of entries in buffer (nonnegative integer)
origin_datatype: - datatype of each buffer entry (handle)
result_addr: - initial address of result buffer (choice)
result_count: - number of entries in result buffer (non-negative integer)
result_datatype: - datatype of each entry in result buffer (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: - datatype of each entry in target buffer (handle)
op: - predefined reduce operation (handle)
win: - window object (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 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 guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.