MPI_Accumulate(3) Open MPI MPI_Accumulate(3)
NAME
MPI_Accumulate, MPI_Raccumulate - Combines the contents of the origin
buffer with that of a target buffer.
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Accumulate(const void *origin_addr, int origin_count,
MPI_Datatype origin_datatype, int target_rank,
MPI_Aint target_disp, int target_count,
MPI_Datatype target_datatype, MPI_Op op, MPI_Win win)
int MPI_Raccumulate(const void *origin_addr, int origin_count,
MPI_Datatype origin_datatype, int target_rank,
MPI_Aint target_disp, int target_count,
MPI_Datatype target_datatype, MPI_Op op, MPI_Win win,
MPI_Request *request)
Fortran Syntax (see FORTRAN 77 NOTES)
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_ACCUMULATE(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK,
TARGET_DISP, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, IERROR)
<type> ORIGIN_ADDR(*)
INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK, TARGET_COUNT,
TARGET_DATATYPE, OP, WIN, IERROR
MPI_RACCUMULATE(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK,
TARGET_DISP, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, REQUEST, IERROR)
<type> ORIGIN_ADDR(*)
INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK, TARGET_COUNT,
TARGET_DATATYPE, OP, WIN, REQUEST, IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Accumulate(origin_addr, origin_count, origin_datatype, target_rank,
target_disp, target_count, target_datatype, op, win, ierror)
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: origin_addr
INTEGER, INTENT(IN) :: origin_count, target_rank, target_count
TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype
INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
TYPE(MPI_Op), INTENT(IN) :: op
TYPE(MPI_Win), INTENT(IN) :: win
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_Raccumulate(origin_addr, origin_count, origin_datatype, target_rank,
target_disp, target_count, target_datatype, op, win, request,
ierror)
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: origin_addr
INTEGER, INTENT(IN) :: origin_count, target_rank, target_count
TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype
INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
TYPE(MPI_Op), INTENT(IN) :: op
TYPE(MPI_Win), INTENT(IN) :: win
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
C++ Syntax
#include <mpi.h>
void MPI::Win::Accumulate(const void* origin_addr, int origin_count,
const MPI::Datatype& origin_datatype, int target_rank,
MPI::Aint target_disp, int target_count, const MPI::Datatype&
target_datatype, const MPI::Op& op) const
INPUT PARAMETERS
origin_addr
Initial address of buffer (choice).
origin_count
Number of entries in buffer (nonnegative integer).
origin_datatype
Data type of each buffer entry (handle).
target_rank
Rank of target (nonnegative integer).
target_disp
Displacement from start of window to beginning of target buf-
fer (nonnegative integer).
target_count
Number of entries in target buffer (nonnegative integer).
target_datatype
Data type of each entry in target buffer (handle).
op Reduce operation (handle).
win Window object (handle).
OUTPUT PARAMETER
MPI_Raccumulate: RMA request
IERROR Fortran only: Error status (integer).
DESCRIPTION
MPI_Accumulate is a function used for one-sided MPI communication that
adds the contents of the origin buffer (as defined by origin_addr, ori-
gin_count, and origin_datatype) to the buffer specified by the argu-
ments target_count and target_datatype, at offset target_disp, in the
target window specified by target_rank and win, using the operation op.
The target window can only be accessed by processes within the same
node. This is similar to MPI_Put, except that data is combined into the
target area instead of overwriting it.
Any of the predefined operations for MPI_Reduce can be used. User-de-
fined functions cannot be used. For example, if op is MPI_SUM, each el-
ement of the origin buffer is added to the corresponding element in the
target, replacing the former value in the target.
Each datatype argument must be a predefined data type or a derived data
type, where all basic components are of the same predefined data type.
Both datatype arguments must be constructed from the same predefined
data type. The operation op applies to elements of that predefined
type. The target_datatype argument must not specify overlapping en-
tries, and the target buffer must fit in the target window.
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.
MPI_Raccumulate is similar to MPI_Accumulate, except that it allocates
a communication request object and associates it with the request han-
dle (the argument request) that can be used to wait or test for comple-
tion. The completion of an MPI_Raccumulate operation indicates that the
origin_addr buffer is free to be updated. It does not indicate that the
operation has completed at the target window.
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
MPI_Put is a special case of MPI_Accumulate, with the operation MPI_RE-
PLACE. Note, however, that MPI_Put and MPI_Accumulate have different
constraints on concurrent updates.
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_Accumulate 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. C++ func-
tions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
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_Put MPI_Get_accumulate MPI_Reduce
4.1.2 Nov 24, 2021 MPI_Accumulate(3)
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