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

.SH NAME

MPI_Fetch_and_op \-  Perform one-sided read-modify-write. 

.SH SYNOPSIS

.nf

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)

.fi

Accumulate one element of type 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 result_addr 

- initial address of result buffer (choice)

.PD 1

.PD 0

.TP

.B datatype 

- datatype of the entry in origin, result, and target buffers (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 (non-negative integer)

.PD 1

.PD 0

.TP

.B op 

- 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 generic functionality of 

.I MPI_Get_accumulate

might limit the performance of

fetch-and-increment or fetch-and-add calls that might be supported by special

hardware operations. 

.I MPI_Fetch_and_op

thus allows for a fast implementation

of a commonly used subset of the functionality of 

.I MPI_Get_accumulate

\&.

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

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. The

datatype argument must be a predefined datatype.

.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_OP 

- Invalid operation.  MPI operations (objects of type 

.I MPI_Op

)

must either be one of the predefined operations (e.g., 

.I MPI_SUM

) or

created with 

.I MPI_Op_create

\&.

.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_Get_accumulate

.br