anchor.diff:    g = 0
     g(1) = PTread_d(config, 'g')
     bufferlength = PTread_i(config, 'buffer_length')
  +  randomisation_length = PTread_i(config, 'randomisation_length')
  +  max_speed = PTread_d(config,'max_speed')
     prob = PTread_d(config,'probability')
   
     number_of_angles = PTread_i(config, 'number_of_angles')
     L = PTread_ivec(config, 'L', 3)
  -  L(1) = L(1) + bufferlength
  +  L(1) = L(1) + bufferlength + randomisation_length
     
     rho = PTread_i(config, 'rho')
     N = rho *L(1)*L(2)*L(3)
  
positive.code: 
    double precision :: g(3) !gravity
    logical :: fixed, on_track, stopped,order
    integer :: bufferlength
    integer :: steps_fixed
    fixed = .true.
    on_track = .true.
  
negative.code:   colloids% pos(3,:) = solvent_cells% edges(3)/2.d0
  
    if (order) then
       colloids% pos(1,1) = sigma_C*2**(1.d0/6.d0) + 1 + randomisation_length
       colloids% pos(1,2) = colloids% pos(1,1) + d
       colloids% pos(2,:) = solvent_cells% edges(2)/2.d0 + 1.5d0*maxval([sigma_C,sigma_N])
    else
       colloids% pos(1,2) = sigma_N*2**(1.d0/6.d0) + 1 + randomisation_length
       colloids% pos(1,1) = colloids% pos(1,2) + d
       colloids% pos(2,:) = solvent_cells% edges(2)/2.d0 + 1.5d0*maxval([sigma_C,sigma_N])
    end if
  