anchor.diff:  
               root_det = decode_det(root_det_f)
   
  +            ! < D | H | D_i^a > = < i | h(a) | a > + \sum_j < ij || aj >
  +
               ! One electron operator
               hmatel = hmatel + get_one_e_int(excitation%from_orb(1), excitation%to_orb(1)) 
   
  
positive.code:         hmatel = 0.0_dp
  
          select case(excitation%nexcit)
          case(0)
  
              root_det = decode_det(root_det_f)
  
              ! One electron operator
              do i = 1, nel
  
negative.code:         integer :: i
   
          do i = 1, ncol
              ! y = H x,
              ! where H is the Hamiltonian matrix, x is the input Lanczos vector
              ! and y the output Lanczos vector.
              call dsymv('U', nrow, 1.0_dp, hamil, nrow, xin(:,i), 1, 0.0_dp, yout(:,i), 1)
          end do
   
  