anchor.diff:      Smin                 = S_min
       Smax                 = S_max
   
  -    S_center             = (Smin+Smax)/2.
  +    S_center             = (Smin + Smax) / 2._x_precision
  +
       j = 0
  +
       call variables(T, Smin, Omega, f_min, optical_depth, tau_eff)
   
       call variables(T, Smax, Omega, f_max, optical_depth, tau_eff)
  
positive.code:     integer                                  ,intent(out) :: index_scp
      real(kind = x_precision)                 ,intent(out) :: sigma_c_thin
      real(kind = x_precision)                 ,intent(out) :: temp_c_thin
   !____________________________________________________________________________________
      integer                                               :: i
  
  
  
negative.code: 
      real(kind = x_precision),dimension(nb_it),intent(out) :: sigma_real
      real(kind = x_precision),dimension(nb_it),intent(out) :: temp_real
      !-----------------------------------------------------------------------
  
      integer                                               :: i
  
      do i = 1,index_scp
        sigma_real(i) = sigma_real_thick(i)
  