anchor.diff:          call elem_vx% append(vx% data, i, i*tau)
           call elem_vx_count% append(vx% count, i, i*tau)
           call vx% reset()
  -     end if
  -
  -     com_pos = ( colloids%pos(:,1)+colloids%image(:,1)*solvent_cells%edges + &
  -          colloids%pos(:,2)+colloids%image(:,2)*solvent_cells%edges)
  -
  -     if ((.not. fixed) .and. (.not. on_track)) then
  -        call msd%add(i-i_release-1, correlate_block_distsq, xvec=com_pos)
        end if
   
        call varia%tic()
  
positive.code:   double precision :: kin_e, temperature
    integer, dimension(N_species) :: n_solvent, catalytic_change, bulk_change
    type(h5md_element_t) :: n_solvent_el, catalytic_change_el, bulk_change_el
  
    double precision :: colloid_pos(3,2)
    double precision :: com_pos(3)
  
negative.code: 
    i_release = 1
    i = 0
    i_block = 0
    write(*,*) 'Running for', N_loop, 'loops'
    !start RMPCDMD
    setup: do while (.not. stopped)
  