anchor.diff:  
                   it = get_thread_id()
                   iexcip_pos = 0
  +                seen_D0 = .false.
                   
                   !$omp do schedule(dynamic,200) 
  -                do iattempt = 1, selection_data%nclusters
  +                do iattempt = 1, selection_data%nsingle_excitors + selection_data%nstochastic_clusters
                       if (iattempt <= selection_data%nsingle_excitors) then
                           ! As noncomposite clusters can't be above truncation level or linked-only all can accumulate +
                           ! propagate. Only need to check not selecting the reference as we treat it separately.
  
positive.code:                 end do
                  !$omp end do
  
                  seen_D0 = .false.
  
                  !$omp do schedule(dynamic, 200)
                  do iattempt = selection_data%nsingle_excitors + selection_data%nstochastic_clusters+1, selection_data%nclusters
                      ! We just select the empty cluster.
  
negative.code:                     ! probability by nprocs.  See comments in select_cluster
                      ! for more details.
                      if (.not. seen_D0) then
                          ! This is the first time this thread is spawning from D0 in this block of iterations
                          ! so it needs to be converted into a det_info_t object for the excitation
                          ! generators. On subsequent calls, cdet does not need to change.
                          
  