MPI_Fetch_and_op(3) Open MPI MPI_Fetch_and_op(3)
NAME
MPI_Fetch_and_op - Combines the contents of the origin buffer with that
of a target buffer and returns the target buffer value.
SYNTAX
C Syntax
#include <mpi.h>
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)
Fortran Syntax (see FORTRAN 77 NOTES)
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FETCH_AND_OP(ORIGIN_ADDR, RESULT_ADDR, DATATYPE, TARGET_RANK,
TARGET_DISP, OP, WIN, IERROR)
<type> ORIGIN_ADDR, RESULT_ADDR(*)
INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
INTEGER DATATYPE, TARGET_RANK, OP, WIN, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Fetch_and_op(origin_addr, result_addr, datatype, target_rank,
target_disp, op, win, ierror)
TYPE(*), DIMENSION(..), INTENT(IN) :: origin_addr
TYPE(*), DIMENSION(..) :: result_addr
TYPE(MPI_Datatype), INTENT(IN) :: datatype
INTEGER, INTENT(IN) :: target_rank
INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
TYPE(MPI_Op), INTENET(IN) :: op
TYPE(MPI_Win), INTENT(IN) :: win
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
INPUT PARAMETERS
origin_addr
Initial address of buffer (choice).
result_addr
Initial address of result buffer (choice).
datatype Data type of the entry in origin, result, and target buffers
(handle).
target_rank
Rank of target (nonnegative integer).
target_disp
Displacement from start of window to beginning of target buf-
fer (nonnegative integer).
op Reduce operation (handle).
win Window object (handle).
OUTPUT PARAMETER
IERROR Fortran only: Error status (integer).
DESCRIPTION
Accumulate one element of type datatype from the origin buffer (ori-
gin_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 contents of the target buffer before
the accumulation.
The origin and result buffers (origin_addr and result_addr) must be
disjoint. Any of the predefined operations for MPI_Rreduce, as well as
MPI_NO_OP or MPI_REPLACE, can be specified as op; user-defined func-
tions cannot be used. The datatype argument must be a predefined
datatype. The operation is executed atomically.
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 op-
eration is performed on the target buffer.
FORTRAN 77 NOTES
The MPI standard prescribes portable Fortran syntax for the TARGET_DISP
argument only for Fortran 90. FORTRAN 77 users may use the non-porta-
ble syntax
INTEGER*MPI_ADDRESS_KIND TARGET_DISP
where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the
length of the declared integer in bytes.
NOTES
It is the user's responsibility to guarantee that, when using the accu-
mulate functions, the target displacement argument is such that ac-
cesses to the window are properly aligned according to the data type
arguments in the call to the MPI_Fetch_and_op function.
ERRORS
Almost all MPI routines return an error value; C routines as the value
of the function and Fortran routines in the last argument.
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
MPI_Comm_set_errhandler; 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.
SEE ALSO
MPI_Get_accumulate
MPI_Reduce
4.1.2 Nov 24, 2021 MPI_Fetch_and_op(3)
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