anchor.diff:          type(dSFMT_t) :: rng
           integer :: ref_det, ndets
           integer(i0), allocatable :: dets(:,:)
  +        real(p) :: H0i, Hii
   
           call init_simple_fciqmc(sys, ndets, dets, ref_det)
   
  
positive.code:                 ! Consider all walkers.
                  do iwalker = 1, ndets
  
                      ! It is much easier to evaluate the projected energy at the
                      ! start of the FCIQMC cycle than at the end.
                      call simple_update_proj_energy(ref_det, iwalker, proj_energy)
  
                      ! Simulate spawning.
                      do ipart = 1, abs(walker_population(1,iwalker))
  
negative.code: 
      end subroutine attempt_spawn
  
      subroutine simple_death(rng, Hii, pop)
  
          ! Simulate cloning/death part of FCIQMC algorithm.
          ! In:
          !    Hii: diagonal matrix element, <D_i|H|D_i>
          ! In/Out:
          !    rng: random number generator.
          !    pop: population on |D_i>.  On output, the population is updated from applying
          !         the death step.
  
          type(dSFMT_t), intent(inout) :: rng
          real(p), intent(in) :: Hii
          integer(int_p), intent(inout) :: pop
  
          integer :: nkill
          real(p) :: rate
  