anchor.diff:                  end if
                end if
   
  +             ! Sample a random optical depth and propagate that optical depth
                call random_exp(tau)
  -
  -             ! Propagate the optical depth sampled
                call grid_integrate(p,tau,tau_achieved)
   
                if(p%reabsorbed) then
  
positive.code:     ! Optical depth to travel
      real(dp) :: tau
  
      ! Used for the forced first interaction
      real(dp) :: tau_escape, weight
      type(photon) :: p_tmp
      logical :: killed
  
      ! REMOVE
      real(dp) :: tau_achieved
  
  
negative.code:              ! If this is not the first interaction, and the user requested to
               ! use the MRW, do the MRW to get out of the optically thick region
  
               if(use_mrw.and.interactions > 1) then
                  do mrw_steps=1,n_mrw_max
                     if(tau_inv_planck_to_closest_wall(p) > mrw_gamma) then
                        call grid_do_mrw(p)
  