anchor.diff:      ! i-FCIQMC). The i-th bit is set if the determinant is not an initiator in
       ! space i.
       integer :: initiator_flag
  +    ! \sum_i F_i - F_0, where F_i is the single-particle eigenvalue of the i-th occupied orbital 
  +    ! and F_0 is the corresponding sum for the reference determinant.
  +    real(p) :: fock_sum
       ! Pointer (never allocated) to corresponding elements in particle_t%dat array.
       real(p), pointer :: data(:) => NULL()
       ! Pointer to an existing cluster_t variable.  Used *only* in CCMC and so
  
positive.code: 
      end subroutine update_sys_spin_info
  
      pure function sum_sp_eigenvalues(sys, occ_list) result(spe_sum)
  
          ! In:
          !    sys: system being studied.
  
negative.code:             spe_sum = spe_sum + sys%basis%basis_fns(occ_list(iorb))%sp_eigv
          end do
  
      end function sum_sp_eigenvalues_occ_list
  
      pure function sum_sp_eigenvalues_bit_string(sys, f) result(spe_sum)
  
          ! In:
          !    sys: system being studied.
          !    f: bit-string representation of a determinant.
          ! Returns:
          !    Sum of the single particle energies.
  
          use system, only: sys_t
  
          real(p) :: spe_sum
          type(sys_t), intent(in) :: sys
          integer(i0), intent(in) :: f(:)
          integer :: occ(sys%nel)
  
          call decode_det(sys%basis, f, occ)
          spe_sum = sum_sp_eigenvalues_occ_list(sys, occ)
  
      end function sum_sp_eigenvalues_bit_string
  
  end module determinants
  