NAME

       MPI_Fetch_and_op -  Perform one-sided read-modify-write.

SYNOPSIS

       int MPI_Fetch_and_op(const void *origin_addr, void *result_addr,
               MPI_Datatype datatype, int target_rank, MPI_Aint target_disp,
               MPI_Op op, MPI_Win win)

       Accumulate one element of type datatype from the origin buffer (origin_addr) to the buffer
       at offset target_disp, in the target window specified by target_rank and  win,  using  the
       operation  op and return in the result buffer result_addr the content of the target buffer
       before the accumulation.

INPUT PARAMETERS

       origin_addr
              - initial address of buffer (choice)
       result_addr
              - initial address of result buffer (choice)
       datatype
              - datatype of the entry in origin, result, and target buffers (handle)
       target_rank
              - rank of target (nonnegative integer)
       target_disp
              - displacement from start of window to beginning  of  target  buffer  (non-negative
              integer)
       op     - reduce operation (handle)
       win    - window object (handle)

NOTES

       This operations is atomic with respect to other "accumulate" operations.

       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 .

       The origin and result buffers (origin_addr and result_addr) must be disjoint.  Any of  the
       predefined  operations  for  MPI_Reduce  ,  as  well  as MPI_NO_OP or MPI_REPLACE , can be
       specified as op; user-defined functions cannot be used. The datatype argument  must  be  a
       predefined datatype.

NOTES FOR FORTRAN

       All  MPI  routines  in  Fortran  (except  for MPI_WTIME and MPI_WTICK ) have an additional
       argument ierr at the end of the argument list.  ierr  is  an  integer  and  has  the  same
       meaning  as  the  return  value  of  the  routine  in  C.   In  Fortran,  MPI routines are
       subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value;  C  routines  as
       the  value of the function and Fortran routines in the last argument.  Before the value is
       returned, the current MPI error handler is called.  By default, this error handler  aborts
       the  MPI  job.   The  error  handler  may  be  changed  with  MPI_Comm_set_errhandler (for
       communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler  (for  RMA
       windows).   The  MPI-1  routine  MPI_Errhandler_set may be used but its use is deprecated.
       The predefined error handler MPI_ERRORS_RETURN may be used to cause  error  values  to  be
       returned.   Note  that  MPI  does  not  guarentee that an MPI program can continue past an
       error; however, MPI implementations will attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_ARG
              - Invalid argument.  Some argument is invalid and is not identified by  a  specific
              error class (e.g., MPI_ERR_RANK ).
       MPI_ERR_COUNT
              - Invalid count argument.  Count arguments must be non-negative; a count of zero is
              often valid.
       MPI_ERR_OP
              - Invalid operation.  MPI operations (objects of type MPI_Op ) must either  be  one
              of the predefined operations (e.g., MPI_SUM ) or created with MPI_Op_create .

       MPI_ERR_RANK
              -  Invalid  source or destination rank.  Ranks must be between zero and the size of
              the  communicator  minus  one;  ranks  in  a  receive  (  MPI_Recv  ,  MPI_Irecv  ,
              MPI_Sendrecv , etc.) may also be MPI_ANY_SOURCE .

       MPI_ERR_TYPE
              -   Invalid   datatype   argument.    May   be  an  uncommitted  MPI_Datatype  (see
              MPI_Type_commit ).
       MPI_ERR_WIN
              - Invalid MPI window object

SEE ALSO

       MPI_Get_accumulate

LOCATION

       src/mpi/rma/fetch_and_op.c

                                            4/24/2013                         MPI_Fetch_and_op(3)