anchor.diff:      fpa_amax = fpa(amax)
   
       ! recompute fxs
  -    fxs = exp(lfwa(xs))
  +    fxs = exp(log_fwa(xs))
   
       ! re-compute a reasonable integration range
       alpha1 = log(minval(xs, fxs > small_number))
  
positive.code:     real(real64) :: a
  
      a = exp(x)
      nrm_func = exp(lfwa(a))  * a
      
    end function nrm_func
  
  
negative.code:     end do
      xs = exp(xs)
      
      fxs = log_fwa(xs)
      ! find amax such that the weight in the integral - fwa(alpha) - is maximal
      i = maxloc(fxs,1,fxs < largest)
      amax = xs(i)
  