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)

       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

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  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).

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, 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. 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-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.

       MPI_Raccumulate is similar to MPI_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_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-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.

NOTES

       MPI_Put is a special  case  of  MPI_Accumulate,  with  the  operation  MPI_REPLACE.  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 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_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++ functions 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