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)

INPUT PARAMETERS

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

OUTPUT PARAMETERS

       result_addr
              - initial address of result buffer (choice)

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 guarantee 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_DISP
              -
       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.  Additionally, this error can occur if an  uncommitted
              MPI_Datatype (see MPI_Type_commit ) is used in a communication call.
       MPI_ERR_WIN
              - Invalid MPI window object
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

SEE ALSO

       MPI_Get_accumulate

                                             2/9/2024                         MPI_Fetch_and_op(3)