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.TH "MPI_RACCUMULATE" "3" "May 30, 2025" "" "Open MPI"
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.INDENT 0.0
.INDENT 3.5
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.sp
\fI\%MPI_Accumulate\fP, \fI\%MPI_Raccumulate\fP \- Combines the contents of the
origin buffer with that of a target buffer.
.SH SYNTAX
.SS C Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#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)
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
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
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran 2008 Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
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
.ft P
.fi
.UNINDENT
.UNINDENT
.SH INPUT PARAMETERS
.INDENT 0.0
.IP \(bu 2
\fBorigin_addr\fP: Initial address of buffer (choice).
.IP \(bu 2
\fBorigin_count\fP: Number of entries in buffer (nonnegative integer).
.IP \(bu 2
\fBorigin_datatype\fP: Data type of each buffer entry (handle).
.IP \(bu 2
\fBtarget_rank\fP: Rank of target (nonnegative integer).
.IP \(bu 2
\fBtarget_disp\fP: Displacement from start of window to beginning of target buffer (nonnegative integer).
.IP \(bu 2
\fBtarget_count\fP: Number of entries in target buffer (nonnegative integer).
.IP \(bu 2
\fBtarget_datatype\fP: Data type of each entry in target buffer (handle).
.IP \(bu 2
\fBop\fP: Reduce operation (handle).
.IP \(bu 2
\fBwin\fP: Window object (handle).
.UNINDENT
.SH OUTPUT PARAMETER
.INDENT 0.0
.IP \(bu 2
\fBMPI_Raccumulate\fP:  RMA request
.IP \(bu 2
\fBierror\fP: Fortran only: Error status (integer).
.UNINDENT
.SH DESCRIPTION
.sp
\fI\%MPI_Accumulate\fP is a function used for one\-sided MPI communication
that adds the contents of the origin buffer (as defined by
\fIorigin_addr\fP, \fIorigin_count\fP, and \fIorigin_datatype\fP) to the buffer
specified by the arguments \fItarget_count\fP and \fItarget_datatype\fP, at
offset \fItarget_disp\fP, in the target window specified by \fItarget_rank\fP
and \fIwin\fP, using the operation \fIop\fP\&. The target window can only be
accessed by processes within the same node. This is similar to \fI\%MPI_Put\fP,
except that data is combined into the target area instead of overwriting
it.
.sp
Any of the predefined operations for \fI\%MPI_Reduce\fP can be used.
User\-defined functions cannot be used. For example, if \fIop\fP 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.
.sp
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 \fIop\fP applies to elements of that predefined
type. The \fItarget_datatype\fP argument must not specify overlapping
entries, and the target buffer must fit in the target window.
.sp
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.
.sp
\fI\%MPI_Raccumulate\fP is similar to \fI\%MPI_Accumulate\fP, except that it
allocates a communication request object and associates it with the
request handle (the argument \fIrequest\fP) that can be used to wait or test
for completion. The completion of an \fI\%MPI_Raccumulate\fP operation
indicates that the \fIorigin_addr\fP buffer is free to be updated. It does
not indicate that the operation has completed at the target window.
.SH NOTES
.sp
\fI\%MPI_Put\fP is a special case of \fI\%MPI_Accumulate\fP, with the operation
MPI_REPLACE. Note, however, that \fI\%MPI_Put\fP and \fI\%MPI_Accumulate\fP have
different constraints on concurrent updates.
.sp
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 \fI\%MPI_Accumulate\fP function.
.SH ERRORS
.sp
Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
.sp
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
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
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.
.sp
Open MPI includes three predefined error handlers that can be used:
.INDENT 0.0
.IP \(bu 2
\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
.IP \(bu 2
\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP 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.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
.UNINDENT
.sp
MPI applications can also implement their own error handlers by calling:
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
.UNINDENT
.sp
Note that MPI does not guarantee that an MPI program can continue past
an error.
.sp
See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
.sp
See the Error Handling section of the MPI\-3.1 standard for
more information.
.sp
\fBSEE ALSO:\fP
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.INDENT 3.5
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.IP \(bu 2
\fI\%MPI_Put\fP
.IP \(bu 2
\fI\%MPI_Get_accumulate\fP
.IP \(bu 2
\fI\%MPI_Reduce\fP
.UNINDENT
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.SH COPYRIGHT
2003-2025, The Open MPI Community
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