subroutine sum_with_use(x, res)
use precision
implicit none
real(kind=rk), intent(in) :: x(:)
real(kind=rk), intent(out) :: res
integer :: i
!print *, "size(x) = ", size(x)
res = 0.0
do i = 1, size(x)
res = res + x(i)
enddo
end subroutine