oracular (3) MPI_Accumulate.openmpi.3.gz

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 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