anchor.diff:  ! They are thrown away after these calculation has been performed on them.
   logical :: calc_inst_rdm = .false.
   
  -! The length of the spawning array for RDMs. Each RDM calculated has the same
  -! length array.
  -integer :: spawned_rdm_length
  -
   ! If true then calculate the concurrence for reduced density matrix of two sites.
   logical :: doing_concurrence = .false.
   
  
positive.code:     ! determinant's population in order to be accepted as the new reference
      ! determinant.
      real(p) :: ref_det_factor = 1.50_p
      ! Also start with D0_population on i_s|D_0>, where i_s is the spin-version
      ! operator.  This is only done if no restart file is used *and* |D_0> is not
      ! a closed shell determinant.
      logical :: init_spin_inv_D0 = .false.
  end type reference_t
  
  ! Spawned lists for rdms.
  
negative.code:     type(rdm_spawn_t), allocatable :: rdm_spawn(:)
      ! The total number of rdms beings calculated.
      integer :: nrdms
      ! The length of the spawning array for RDMs. Each RDM calculated has the same
      ! length array.
      integer :: spawned_rdm_length
      ! This stores all the information for the various RDMs that the user asks
      ! to be calculated. Each element of this array corresponds to one of these RDMs.
      type(rdm_t), allocatable :: rdms(:)
  