anchor.diff:                              end if
   
                           ! For OpenMP scalability, have this test inside a single loop rather
  -                        ! than attempt to parallelise over three separate loops.
  -                        else if (iattempt <= selection_data%nsingle_excitors + selection_data%nstochastic_clusters) then
  +                        ! than attempt to parallelise over two separate loops.
  +                        else
                               if (ccmc_in%even_selection) then
                                   call select_cluster_truncated(rng(it), sys, qs%psip_list, qs%ref%f0, &
                                                               ccmc_in%linked, selection_data%nstochastic_clusters, D0_normalisation, &
  
positive.code:                                                 ccmc_in%even_selection)
                      call zero_ps_stats(ps_stats, qs%excit_gen_data%p_single_double%rep_accum%overflow_loc)
  
                      proj_energy_cycle = cmplx(0.0, 0.0, p)
                      D0_population_cycle = cmplx(0.0, 0.0, p)
  
                      ! OpenMP chunk size determined completely empirically from a single
                      ! test.  Please feel free to improve...
  
negative.code:                     call init_mc_cycle(qs%psip_list, qs%spawn_store%spawn, qs%estimators(1)%nattempts, ndeath, &
                                         min_attempts=nint(abs(D0_normalisation), kind=int_64), &
                                         complx=sys%read_in%comp)
  
                      ! Find cumulative population...
                      ! NOTE: for simplicity we only consider the integer part of the population on each excitor.
                      ! (Populations under 1 are stochastically rounded in the annihilation process, so each excitor in the list has
  