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MPI_Accumulate(3) man page (version 1.3.4)

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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).
       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-
       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.

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_REPLACE. Note, however, that MPI_Put and MPI_Accumulate  have  dif-
       ferent 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
       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++ 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

1.3.4                            Nov 11, 2009                MPI_Accumulate(3)

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