anchor.diff:                              ! If this condition is met then there will only be
                               ! one det in this symmetry sector, so don't attempt
                               ! to spawn.
  -                            if (.not. ((sys%nel == 0) .or. (sys%nel == sys%basis%nbasis))) then
  +                            if (.not. ((sys_copy%nel == 0) .or. (sys_copy%nel == sys_copy%basis%nbasis))) then
                                   nattempts_current_det = decide_nattempts(rng, real_population(ireplica))
                                   do iparticle = 1, nattempts_current_det
                                       ! When using importance sampling in DMQMC we
  
positive.code:         ! times, to accumulate statistics for each value for beta.
  
          ! In:
          !    restart_in: input options for HDF5 restart files.
          !    load_bal_in: input options for load balancing.
          !    reference_in: current reference determinant.  If not set (ie
          !       components allocated) then a best guess is made based upon the
          !       desired spin/symmetry.
          ! In/Out:
          !    sys: system being studied.  NOTE: if modified inside a procedure,
          !         it should be returned in its original (ie unmodified state)
          !         at the end of the procedure.
          !    qmc_in: input options relating to QMC methods.
          !    dmqmc_in: input options relating to DMQMC.
          !    dmqmc_estimates: type containing all DMQMC estimates.
  
negative.code: 
                          ! f points to the bitstring that is spawning, f2 to the
                          ! other bit string.
                          cdet1%f => qs%psip_list%states(:sys_copy%basis%string_len,idet)
                          cdet1%f2 => qs%psip_list%states((sys_copy%basis%string_len+1):(2*sys_copy%basis%string_len),idet)
                          cdet1%data => qs%psip_list%dat(:,idet)
                          cdet2%f => qs%psip_list%states((sys_copy%basis%string_len+1):(2*sys_copy%basis%string_len),idet)
                          cdet2%f2 => qs%psip_list%states(:sys_copy%basis%string_len,idet)
  
                          ! Decode and store the the relevant information for
                          ! both bitstrings. Both of these bitstrings are required
  