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MPI_Get_accumulate, MPI_Rget_accumulate - Combines the contents
of the origin buffer with that of a target buffer and returns the target
buffer value.
#include <mpi.h>
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)
int MPI_Rget_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,
MPI_Request *request)
INCLUDE ’mpif.h’
MPI_GET_ACCUMULATE(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, RESULT_ADDR,
RESULT_COUNT, RESULT_DATATYPE, TARGET_RANK, TARGET_DISP, TARGET_COUNT,
TARGET_DATATYPE, OP, WIN, IERROR)
<type> ORIGIN_ADDR, RESULT_ADDR(*)
INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_COUNT, TARGET_DATATYPE,
TARGET_RANK, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, IERROR
MPI_RGET_ACCUMULATE(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, RESULT_ADDR,
RESULT_COUNT, RESULT_DATATYPE, TARGET_RANK, TARGET_DISP, TARGET_COUNT,
TARGET_DATATYPE, OP, WIN, REQUEST, IERROR)
<type> ORIGIN_ADDR, RESULT_ADDR(*)
INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_COUNT, TARGET_DATATYPE,
TARGET_RANK, TARGET_COUNT, TARGET_DATATYPE, OP, WIN, REQUEST, IERROR
- 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).
- result_addr
- Initial address of result
buffer (choice).
- result_count
- Number of entries in result buffer (nonnegative
integer).
- result_datatype
- Data type of each result buffer entry (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
- Data type of each entry in target buffer (handle).
- op
- Reduce operation (handle).
- win
- Window object (handle).
- MPI_Rget_accumulate: RMA request
- IERROR
- Fortran only: Error status (integer).
MPI_Get_accumulate
is a function used for one-sided MPI communication that adds the contents
of the origin buffer (as defined by origin_addr, origin_count, and origin_datatype)
to the buffer specified by the arguments target_count and target_datatype,
at offset target_disp, in the target window specified by target_rank and
win, using the operation op. MPI_Get_accumulate returns in the result buffer
result_addr the contents of the target buffer before the accumulation.
Any
of the predefined operations for MPI_Reduce, as well as MPI_NO_OP, can
be used. User-defined functions cannot be used. For example, if op is MPI_SUM,
each element 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 entries, 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.
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 operation
is performed on the target buffer.
MPI_Rget_accumulate is similar to MPI_Get_accumulate,
except that it allocates a communication request object and associates
it with the request handle (the argument request) that can be used to wait
or test for completion. The completion of an MPI_Rget_accumulate operation
indicates that the data is available in the result buffer and the origin
buffer is free to be updated. It does not indicate that the operation has
been completed at the target window.
The MPI standard prescribes
portable Fortran syntax for the TARGET_DISP argument only for Fortran 90.
FORTRAN 77 users may use the non-portable 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.
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.
MPI_Get is a special case of MPI_Get_accumulate,
with the operation MPI_NO_OP. Note, however, that MPI_Get and MPI_Get_accumulate
have different constraints on concurrent updates.
It is the user’s responsibility
to guarantee that, when using the accumulate functions, the target displacement
argument is such that accesses to the window are properly aligned according
to the data type arguments in the call to the MPI_Get_accumulate function.
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.
MPI_Put MPI_Get MPI_Accumulate MPI_Fetch_and_op
MPI_Reduce
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