anchor.diff:      type(spawn_t) :: received_list
       ! spawn times of the progeny (only used for ct_fciqmc)
       real(p), allocatable :: spawn_times(:) ! (spawned_walker_length)
  +    ! [review] - FDM: Should this be here? maybe calc?
       ! Rate of spawning.  This is a running total over MC cycles on each processor
       ! until it is summed over processors and averaged over cycles in
       ! update_energy_estimators.
  
positive.code: 
  ! Are we doing a timestep search
  logical :: tau_search = .false.
  !--- Reference determinant ---
  type reference_t
      ! Bit string of reference determinant.
  
negative.code:     integer, allocatable :: flags(:)
  end type semi_stoch_t
  
  ! [review] - FDM: Not sure how to organise semi-stochastic data given that there already exists a semi_stoch_t object.
  !--- Semi-stochastic ---
  enum, bind(c)
      ! This option uses an empty deterministic space, and so turns
  