old_contents: """Demonstrate the Vissio-Lucarini-20 model.
  
  Reproduce Hovmoller diagram Fig 4. in `bib.vissio2020mechanics`.
  """
  import numpy as np
  from matplotlib import pyplot as plt
  
  import dapper.mods as modelling
  from dapper.mods.VL20 import model_instance
  
  VL20 = model_instance(nX=36, F=10, G=0)
  step = modelling.with_rk4(VL20.dxdt, autonom=True)
  simulator = modelling.with_recursion(step, prog="Simulating")
  
  x0 = np.random.rand(72)
  
  dt = 0.05
  xx = simulator(x0, k=22000, t0=0, dt=dt)
  
  plt.figure(1)
  plt.clf()
  plt.contourf(xx[-200:, :], levels=100, cmap='jet')
  plt.colorbar()
  plt.xticks([0, 9, 19, 29, 36, 45, 55, 65], [1, 10, 20, 30, 1, 10, 20, 30])
  plt.yticks(np.arange(0, 220, 20), np.arange(0, 11, 1))
  plt.xlabel(r'$X_k, k = 1, ..., 36$'+' '*15+r'$\theta_k, k = 1, ..., 36$')
  plt.ylabel('time')
  plt.show()
  
new_contents: """Demonstrate the Vissio-Lucarini-20 model.
  
  Reproduce Hovmoller diagram Fig 4. in `bib.vissio2020mechanics`.
  """
  import numpy as np
  from matplotlib import pyplot as plt
  
  import dapper.mods as modelling
  from dapper.mods.VL20 import model_instance
  
  VL20 = model_instance(nX=36, F=10, G=0)
  step = modelling.with_rk4(VL20.dxdt, autonom=True)
  simulator = modelling.with_recursion(step, prog="Simulating")
  
  x0 = np.random.rand(72)
  
  dt = 0.05
  xx = simulator(x0, k=2200, t0=0, dt=dt)
  
  plt.figure(1)
  plt.clf()
  plt.contourf(xx[-200:, :], levels=100, cmap='jet')
  plt.colorbar()
  plt.xticks([0, 9, 19, 29, 36, 45, 55, 65], [1, 10, 20, 30, 1, 10, 20, 30])
  plt.yticks(np.arange(0, 220, 20), np.arange(0, 11, 1))
  plt.xlabel(r'$X_k, k = 1, ..., 36$'+' '*15+r'$\theta_k, k = 1, ..., 36$')
  plt.ylabel('time')
  plt.show()
  
subject: Fix excessive duration