.TH MPI_Get_accumulate 3 "11/12/2019" " " "MPI"

.SH NAME

MPI_Get_accumulate \-  Perform an atomic, one-sided read-and-accumulate operation. 

.SH SYNOPSIS

.nf

int MPI_Get_accumulate(const void *origin_addr, int origin_count,

MPI_Datatype origin_datatype, void *result_addr, int result_count,

MPI_Datatype result_datatype, int target_rank, MPI_Aint target_disp,

int target_count, MPI_Datatype target_datatype, MPI_Op op, MPI_Win win)

.fi

Accumulate origin_count elements of type origin_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.

.SH INPUT PARAMETERS

.PD 0

.TP

.B origin_addr 

- initial address of buffer (choice)

.PD 1

.PD 0

.TP

.B origin_count 

- number of entries in buffer (nonnegative integer)

.PD 1

.PD 0

.TP

.B origin_datatype 

- datatype of each buffer entry (handle)

.PD 1

.PD 0

.TP

.B result_addr 

- initial address of result buffer (choice)

.PD 1

.PD 0

.TP

.B result_count 

- number of entries in result buffer (non-negative integer)

.PD 1

.PD 0

.TP

.B result_datatype 

- datatype of each entry in result buffer (handle)

.PD 1

.PD 0

.TP

.B target_rank 

- rank of target (nonnegative integer)

.PD 1

.PD 0

.TP

.B target_disp 

- displacement from start of window to beginning of target

buffer (nonnegative integer)

.PD 1

.PD 0

.TP

.B target_count 

- number of entries in target buffer (nonnegative integer)

.PD 1

.PD 0

.TP

.B target_datatype 

- datatype of each entry in target buffer (handle)

.PD 1

.PD 0

.TP

.B op 

- predefined reduce operation (handle)

.PD 1

.PD 0

.TP

.B win 

- window object (handle)

.PD 1

.SH NOTES

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

The get and accumulate steps are executed atomically for each basic element in

the datatype (see MPI 3.0 Section 11.7 for details). The predefined operation

.I MPI_REPLACE

provides fetch-and-set behavior.

The origin and result buffers (origin_addr and result_addr) must be disjoint.

Each datatype argument must be a predefined datatype or a derived datatype

where all basic components are of the same predefined datatype. All datatype

arguments must be constructed from the same predefined datatype. The

operation op applies to elements of that predefined type. target_datatype must

not specify overlapping entries, and the target buffer must fit in the target

window or in attached memory in a dynamic window.

Any of the predefined operations for 

.I MPI_Reduce

, as well as 

.I MPI_NO_OP

or

.I MPI_REPLACE

can be specified as op. User-defined functions cannot be used. A

new predefined operation, 

.I MPI_NO_OP

, is defined. It corresponds to the

associative function f (a, b) = a; i.e., the current value in the target memory

is returned in the result buffer at the origin and no operation is performed on

the target buffer. 

.I MPI_NO_OP

can be used only in 

.I MPI_Get_accumulate

,

.I MPI_Rget_accumulate

, and 

.I MPI_Fetch_and_op

\&.

.I MPI_NO_OP

cannot be used in

.I MPI_Accumulate

, 

.I MPI_Raccumulate

, or collective reduction operations, such as

.I MPI_Reduce

and others.

.SH NOTES FOR FORTRAN

All MPI routines in Fortran (except for 

.I MPI_WTIME

and 

.I MPI_WTICK

) have

an additional argument 

.I ierr

at the end of the argument list.  

.I 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

.I call

statement.

All MPI objects (e.g., 

.I MPI_Datatype

, 

.I MPI_Comm

) are of type 

.I INTEGER

in Fortran.

.SH ERRORS

All MPI routines (except 

.I MPI_Wtime

and 

.I 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 

.I MPI_Comm_set_errhandler

(for communicators),

.I MPI_File_set_errhandler

(for files), and 

.I MPI_Win_set_errhandler

(for

RMA windows).  The MPI-1 routine 

.I MPI_Errhandler_set

may be used but

its use is deprecated.  The predefined error handler

.I MPI_ERRORS_RETURN

may be used to cause error values to be returned.

Note that MPI does 

.B not

guarentee that an MPI program can continue past

an error; however, MPI implementations will attempt to continue whenever

possible.

.PD 0

.TP

.B MPI_SUCCESS 

- No error; MPI routine completed successfully.

.PD 1

.PD 0

.TP

.B MPI_ERR_ARG 

- Invalid argument.  Some argument is invalid and is not

identified by a specific error class (e.g., 

.I MPI_ERR_RANK

).

.PD 1

.PD 0

.TP

.B MPI_ERR_COUNT 

- Invalid count argument.  Count arguments must be 

non-negative; a count of zero is often valid.

.PD 1

.PD 0

.TP

.B 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

(

.I MPI_Recv

, 

.I MPI_Irecv

, 

.I MPI_Sendrecv

, etc.) may also be 

.I MPI_ANY_SOURCE

\&.

.PD 1

.PD 0

.TP

.B MPI_ERR_TYPE 

- Invalid datatype argument.  Additionally, this error can

occur if an uncommitted MPI_Datatype (see 

.I MPI_Type_commit

) is used

in a communication call.

.PD 1

.PD 0

.TP

.B MPI_ERR_WIN 

- Invalid MPI window object

.PD 1

.SH SEE ALSO

MPI_Rget_accumulate MPI_Fetch_and_op

.br