anchor.diff:              ! Must be the reference.
               cdet%f = f0
               cluster%excitation_level = 0
  -            cluster%amplitude = D0_normalisation
  +            cluster%amplitude = normalisation
               cluster%cluster_to_det_sign = 1
               if (cluster%amplitude <= initiator_population) then
                   ! Something has gone seriously wrong and the CC
  
positive.code:                 ! As we might select the reference determinant multiple times in
                  ! a cycle, the running total of D0_population is incorrect (by
                  ! a factor of the number of times it was selected).
                  call binary_search(walker_dets, f0, 1, tot_walkers, hit, D0_pos)
                  D0_normalisation = walker_population(1,D0_pos)
  
                  ! Note that 'death' in CCMC creates particles in the spawned
  
negative.code: 
      end subroutine do_ccmc
  
      subroutine select_cluster(rng, nattempts, normalisation, D0_pos, cumulative_excip_pop, tot_excip_pop, max_size, cdet, cluster)
  
          ! Select a random cluster of excitors from the excitors on the
          ! processor.  A cluster of excitors is itself an excitor.  For clarity
  