anchor.diff:      double precision :: loc(3), r, r_P, r_S
   
       logical          :: outer_boundary_test(3)
  +    integer          :: boundary_buf(3), idx(3)
   
       do k = lo(3), hi(3)
          loc(3) = problo(3) + (dble(k) + HALF) * dx(3)
  
positive.code: 
               ! We must ensure that the outermost zones are untagged
               ! due to the Poisson equation boundary conditions.
               ! This is necessary in addition to the above step
               ! because the problem center doesn't always coincide
               ! with the geometric center. However we can avoid this
               ! restriction on symmetric boundaries.
  
               outer_boundary_test = .false.
  
               do n = 1, dim
  
                  if ((physbc_lo(n) .ne. Symmetry) .and. (loc(n) .lt. problo(n) + TWO * dx(n))) then
                     outer_boundary_test(n) = .true.
                  endif
  
                  if ((physbc_hi(n) .ne. Symmetry) .and. (loc(n) .gt. probhi(n) - TWO * dx(n))) then
                     outer_boundary_test(n) = .true.
                  endif
  
  
negative.code: 
      use bl_constants_module, only: ZERO, HALF, TWO
      use meth_params_module, only: NVAR, URHO, UTEMP
      use prob_params_module, only: center, probhi, dim, Symmetry, physbc_lo, physbc_hi, &
                                    n_error_buf, ref_ratio, blocking_factor, domlo_level, domhi_level
      use probdata_module, only: max_tagging_radius, &
                                 max_stellar_tagging_level, &
                                 max_temperature_tagging_level, &
  