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" operations.


The generic functionality of MPI_Get_accumulate might limit the performance of
fetch-and-increment or fetch-and-add calls that might be supported by special
hardware operations. MPI_Fetch_and_op thus allows for a fast implementation
of a commonly used subset of the functionality 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 functions 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 communicators),
MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (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 whenever
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 receive
(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