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MPI_Fetch_and_op(3)		      MPI		   MPI_Fetch_and_op(3)

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"	opera-
       tions.

       The generic functionality of MPI_Get_accumulate might limit the perfor-
       mance of	fetch-and-increment or fetch-and-add calls that	might be  sup-
       ported  by  special  hardware operations.  MPI_Fetch_and_op thus	allows
       for a fast implementation of a commonly used subset of the  functional-
       ity 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	 func-
       tions  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 com-
       municators),  MPI_File_set_errhandler  (for files), and MPI_Win_set_er-
       rhandler	(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	 when-
       ever 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 re-
	      ceive ( 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

				   2/3/2025		   MPI_Fetch_and_op(3)

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