anchor.diff:      Keo = Ke
       erro = errn
       DO g = ng,1,-1
  -
  -        ss0  = 0.d0
  -        ssx1 = 0.d0; ssy1 = 0.d0; ssz1 = 0.d0
  -        ssx2 = 0.d0; ssy2 = 0.d0; ssz2 = 0.d0
   
           !!!Calculate Scattering source
           CALL SSrcAd(g, ss0, ssx1, ssy1, ssz1, ssx2, ssy2, ssz2)
  
positive.code: IMPLICIT NONE
  
  INTEGER, INTENT(IN) :: gt
  REAL, DIMENSION(:), INTENT(INOUT) :: s, sx1, sy1, sz1
  REAL, DIMENSION(:), INTENT(INOUT) :: sx2, sy2, sz2
  
  INTEGER :: h, n
  
  DO h = 1, ng
      DO n = 1, nnod
  
negative.code: p = 0.d0
  DO g= 1, ng
      DO n= 1, nnod
          p(n) = p(n) + f0(n,g) * sigf(n,g) * vdel(n)
      END DO
  END DO
  
  !STOP
  
  ! Normalize to 1.0
  tpow = 0.
  