title: What is the best way to tell openMDAO driver or solver that it is impossible to evaluate the model at some point?
body: <p>Sometimes there are points in a model in which it is impossible to evaluate the objective function, the unknowns or resids. Which is the best way to tell openMDAO that this is an invalid point?</p>
  
  <p>Setting the unknowns and resids to nan, inf or some other way?</p>