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MPI_Accumulate(3OpenMPI)                                                            MPI_Accumulate(3OpenMPI)



NAME
       MPI_Accumulate  - Combines the contents of the origin buffer with that of a target buffer.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Accumulate(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)


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


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
       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_Accumulate  is a function used for one-sided MPI communication that adds the contents of the ori-gin origin
       gin 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 ele-ment element
       ment 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  compo-nents components
       nents 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  tar-get_datatype target_datatype
       get_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 ori-gin. origin.
       gin.



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_Reduce



Open MPI 1.2                                   September 2006                       MPI_Accumulate(3OpenMPI)