But supposed you wanted to write something which showed the state of the computation at each step. Then the model and the view are more intertwined and the model can no longer act as if it "just does it's job" regardless of what view gets tacked onto it later.

Turn the computation data model into something that can be "stepped". That is, instead of   $computation->run(); set it up so that you can do something like

  while ( ! $computation->done() ) {
      $computation->step()
  }
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Assuming the computation data model is playing fair, it'll notify all views that it has changed after each step, giving each view a chance to redraw (or reconfigure itself and redraw). You're going to take a big performance hit, but if the point is to illustrate the computation, so be it.

This is a standard technique in the MVC world.

The process of thinking through how to split a computation into steps, and what state needs to be maintained between steps, can be difficult, but is often be very insightful.