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MPI_Fetch_and_op(3) MPI MPI_Fetch_and_op(3)
MPI_Fetch_and_op - Perform one-sided read-modify-write.
int MPI_Fetch_and_op(const void *origin_addr, void *result_addr,
MPI_Datatype datatype, int target_rank, MPI_Aint target_disp,
MPI_Op op, MPI_Win win)
Accumulate one element of type 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
- initial address of buffer (choice)
- initial address of result buffer (choice)
- datatype of the entry in origin, result, and target buffers
- rank of target (nonnegative integer)
- displacement from start of window to beginning of target
buffer (non-negative integer)
op - reduce operation (handle)
win - window object (handle)
This operations is atomic with respect to other "accumulate"
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 .
The origin and result buffers (origin_addr and result_addr) must be
disjoint. 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. The datatype argument must be a predefined
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
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.
- No error; MPI routine completed successfully.
- Invalid argument. Some argument is invalid and is not
identified by a specific error class (e.g., MPI_ERR_RANK ).
- Invalid count argument. Count arguments must be non-negative;
a count of zero is often valid.
- Invalid operation. MPI operations (objects of type MPI_Op )
must either be one of the predefined operations (e.g., MPI_SUM )
or created with MPI_Op_create .
- 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 .
- Invalid datatype argument. Additionally, this error can occur
if an uncommitted MPI_Datatype (see MPI_Type_commit ) is used in
a communication call.
- Invalid MPI window object