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827Re: [aima-talk] A serious logical error in chapter 2.

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  • Nima Talebi
    Jun 21, 2008
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      I think the mention of `dump', not being in the action list of the agent, as you correctly stated, in this environment at least serves no purpose.

      I think (please correct me if I'm wrong), Dr. Norvig mentions the action of a `dump' only as a means of driving a point home - If allowed to be the designer of it's own performance measure, it could easily make life easy for itself and, as an *example*, enter a loop of clean-->dump-->clean-->dump... and satisfy itself that it is performing extremely well, while in reality, it's doing nothing.

      Here is another example I've come across which may help...

      There was a robotics experiment (reinforcement learning) where a robot had a ball-mouse attached to it behind, and it was `rewarded' for how much the ball rolled *forward*, then allowed to experiment in a room... hopefully to learn to move as fast as possible by itself.

      It was left to explore overnight, and in the morning, it was found sitting at an area in the room where there was a lump on the ground... and what the agent was found doing was this...

      Best way to draw a picture is this - imagine a dog rubbing it's behind on the carpet as to scratch it.

      In effect - that is what it had learned to do. It was (incorrectly) being rewarded because the series of motions it had learned and was carrying was indeed honoring (cheating) the reward system...
       * the ball was rolling forward faster than ever before.

      This is analogous to the vacuum cleaner taking a dump and sucking it backup.  I hope I've answered your question? =)

      Nima

      On Sun, Jun 22, 2008 at 10:58 AM, aydogan_ozgur <aydogan_ozgur@...> wrote:

      In Performance Measures of Chapter 2, Mr. Norvig refutes the goal of
      counting the number of cleaning a square by claiming that the
      cleaner,in which case, can successionly clean and DUMP the dirt of
      the same square, which is clearly worthless.

      However, there is a nontrivial glitch in this proposition. The Actions
      of the cleaner are

      to move right,
      to move left,
      to clean or
      to do nothing.

      In other words, there is no DUMP action, which Mr. Norvig uses to
      refute the proposition. So, I think, he can't just make up another
      action to refute the proposition. I hope, I am not exagerrating the case?

      Thanks for reading.


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