+ subroutine uop( cin, cout, count, datatype )
+ use mpi
+ integer cin(*), cout(*)
+ integer count, datatype
+ integer i
+
+ if (datatype .ne. MPI_INTEGER) then
+ print *, 'Invalid datatype (',datatype,') passed to user_op()'
+ return
+ endif
+
+ do i=1, count
+ cout(i) = cin(i) + cout(i)
+ enddo
+ end
+