\theta)$ in our controller and obtained the same result. This doesn't
      depend at all on our estimate of the mass, and only linearly on our
      estimates of the length and gravity (and if one cannot measure the length
      of the pendulum accurately, then a proper measuring device would make an
      excellent investment).  This is somewhat amazing; we will develop many
      optimization-based algorithms capable of swinging up the pendulum, but it
      will take a lot of work to find one that is as