MPI_ACCUMULATE(3)				     Open MPI					 MPI_ACCUMULATE(3)

MPI_Accumulate,	 MPI_Raccumulate  <#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
	  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

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 <#mpi-put>, except that data is combined into the target area instead
       of overwriting it.

       Any  of	the predefined operations for MPI_Reduce <#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	<#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 <#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.

NOTES
       MPI_Put <#mpi-put> is a special case of MPI_Accumulate, with the operation MPI_REPLACE. Note, however, that
       MPI_Put <#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 return result of the function and  Fortran
       routines in the last argument.

       Before  the error value is returned, the current MPI error handler associated with the communication object
       (e.g., communicator, window, file) is called.  If no communication object is associated with the MPI  call,
       then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When
       MPI_COMM_SELF is not initialized (i.e.,	before	MPI_Init  <#mpi-init>/MPI_Init_thread  <#mpi-init-thread>,
       after  MPI_Finalize  <#mpi-finalize>,  or  when	using the Sessions Model exclusively) the error raises the
       initial error handler. The initial error handler can  be	 changed  by  calling  MPI_Comm_set_errhandler	<#
       mpi-comm-set-errhandler>	 on  MPI_COMM_SELF  when  using the World model, or the mpi_initial_errhandler CLI
       argument	 to  mpiexec  or  info	key   to   MPI_Comm_spawn   <#mpi-comm-spawn>/MPI_Comm_spawn_multiple	<#
       mpi-comm-spawn-multiple>.   If  no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
       error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error  handler  is  called  for  all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT  An  error handler that can be invoked on a communicator, window, file, or session. When
	 called on a communicator, it acts as if MPI_Abort <#mpi-abort> was called on that communicator. If called
	 on a window or file, acts as if MPI_Abort <#mpi-abort> was called on a communicator containing the  group
	 of processes in the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler	 <#mpi-comm-create-errhandler>	   then	    MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	<#mpi-file-create-errhandler>	  then	   MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

       See also:

	  • MPI_Put <#mpi-put>

	  • MPI_Get_accumulate <#mpi-get-accumulate>

	  • MPI_Reduce <#mpi-reduce>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					 MPI_ACCUMULATE(3)
