Loading ...
Sorry, an error occurred while loading the content.

Re: Performance Measure

Expand Messages
  • Ravi Mohan
    Chuck, ... I had replied to you as soon as I saw your email (The reply is duplicated below, Please note the date. Maybe your filters plonked it into your spam
    Message 1 of 5 , Oct 1, 2007
    • 0 Attachment
      Chuck,

      > . Which is correct? I emailed Ravi Mohan
      > about that, but never received a response.


      I had replied to you as soon as I saw your email (The reply is
      duplicated below, Please note the date. Maybe your filters plonked it
      into your spam folder? )


      Regds,
      Ravi

      *********************************************************

      --- Ravi Mohan <magesmail@...> wrote:

      > Date: Mon, 24 Sep 2007 04:10:46 -0700 (PDT)
      > From: Ravi Mohan <magesmail@...>
      > Subject: Re:
      > aima.basic.vaccum.TrivialVaccumEnvironment.java
      > To: Chuck Wolber <chuckw@...>
      >
      > Hi Chuck,
      >
      >
      > > Since the Vaccum cleaner environment referred to
      > in
      > > question 2.7 refers to
      > > the assumptions made on page 36, I am confused at
      > > how a reward of ten
      > > points was associated with cleaning a location?
      > >
      >
      > See Section 3.2 (Example Problems) for where the
      > path
      > cost comes from. I am not sure where I got the
      > performance measure of +10, but it looks reasonable
      > to me.

      > Feel free to alter it to whatever makes sense :-). Any value that is
      nx for n > 1 should work.
      >
      > Thanks,
      > Ravi
      >
      >
      >
      >
      **********************************************************************

      --- In aima-talk@yahoogroups.com, Chuck Wolber <chuckw@...> wrote:
      >
      >
      > This is with regards to AIMA 2nd Ed, page 36.
      >
      > The description says that if a performance penalty of one point is
      > assessed, the agent will fare poorly. I'm at a bit of a loss to explain
      > how the agent could ever perform well in that situation. If, as the
      first
      > bullet indicates, the agent gets one point at each time step for a
      clean
      > square, and loses a point for each movement, wouldn't that mean the
      agent
      > could never possibly score higher than 1 or lower than 0 at the end
      of its
      > run if a peformance penalty is assessed?
      >
      > (This same scenario is referenced in question 2.9, but I believe my
      > question only asks for clarification, not an answer.)
      >
      > ..Chuck..
      >
      >

      >
    • Chuck Wolber
      ... Weird. You re right, I did receive it, at least my mail server logs say so, but it wasn t trapped in my spam folder nor do I recall seeing it in my inbox.
      Message 2 of 5 , Oct 2, 2007
      • 0 Attachment
        On Tue, 2 Oct 2007, Ravi Mohan wrote:

        > > Which is correct? I emailed Ravi Mohan about that, but never received
        > > a response.
        >
        > I had replied to you as soon as I saw your email (The reply is
        > duplicated below, Please note the date. Maybe your filters plonked it
        > into your spam folder? )

        Weird. You're right, I did receive it, at least my mail server logs say
        so, but it wasn't trapped in my spam folder nor do I recall seeing it in
        my inbox.


        > > Since the Vaccum cleaner environment referred to in question 2.7
        > > refers to the assumptions made on page 36, I am confused at how a
        > > reward of ten points was associated with cleaning a location?
        >
        > See Section 3.2 (Example Problems) for where the path cost comes from. I
        > am not sure where I got the performance measure of +10, but it looks
        > reasonable to me.
        >
        > Feel free to alter it to whatever makes sense :-). Any value that is nx
        > for n > 1 should work.

        Thanks, that explains a lot.

        I'm still curious as to what the value of setting the performance penalty
        to -1 where the reward is +1. It seems as if they'll simply cancel each
        other out. Or perhaps I am over thinking it and missing the fact that
        question 2.9 speaks from the standpoint of an agent that cannot possibly
        maximize its performance measure.

        ..Chuck..

        --
        "The idea that any one of us [presidential candidates] can bring about
        this change is a fantasy, it is not the truth! We need you to bring about
        the change on all these issues, we need you involved, we need you taking
        responsibility!"
        --John Edwards
      • Abhijeet Sinha
        Hey, I don t know if i would be able to explain it to you very well, but i would still like to make a try. In the vacuum cleaner agent we assume that the
        Message 3 of 5 , Oct 2, 2007
        • 0 Attachment
          Hey,
                  I don't know if i would be able to explain it to you very well, but i would still like to make a try.

          In the vacuum cleaner agent we assume that the environment consist of two squares. The agent can sense the square in which it is present, and if any dirt is present in that square.
          The first PEAS description says that "Clean squares remain clean"; the agent gets one point for each clean square at each time. If 1000 time steps would be considered then our agent will score anything above 998(if initially  both squares were dirty) to 1000 (if initially none of the squares were dirty).

          Now in the next description, it is proposed that the vacuum-cleaner agent would be wasting energy if it is allowed to move to the other square if both the squares are clean. So very rightly the performance measure deducts one point for moving into a clean square.
          • If the agent starts with both the squares as dirty and then continues for 1000 time steps as before i.e not stopping if both the squares are clean then it would score -ve 998.
          • Similarly if the agent would have started with one of the squares as dirty and continues for 1000 time steps then it would end up in a score of -ve 999.
          So having one more assumption makes out earlier agent ir-rational.
          So the agent function has to be modified. For this agent, we could consider the following agent function:

          function VACUUM_CLEANER_AGENT ( location , state ) returns action
          ka = 0;  internal memory for square A
          kb = 0;  internal memory for square B

          if ( state == dirt ) then return SUCK
          else if ( ka + kb < 2 ) and location = A then {  ka=1 ; return RIGHT }
          else if ( ka + kb < 2 ) and location = B then {  kb=1 ; return LEFT }
          else if ( ka + kb == 2 ) return NOP

          Here we have ka & kb as state memory as said in 2.9

          Abhijeet.


          On 10/2/07, Chuck Wolber <chuckw@...> wrote:


          This is with regards to AIMA 2nd Ed, page 36.

          The description says that if a performance penalty of one point is
          assessed, the agent will fare poorly. I'm at a bit of a loss to explain
          how the agent could ever perform well in that situation. If, as the first
          bullet indicates, the agent gets one point at each time step for a clean
          square, and loses a point for each movement, wouldn't that mean the agent
          could never possibly score higher than 1 or lower than 0 at the end of its
          run if a peformance penalty is assessed?

          (This same scenario is referenced in question 2.9, but I believe my
          question only asks for clarification, not an answer.)

          ..Chuck..

          P.S. The aima-java class TrivialVacuumEnvironment.java awards 10 points
          for a clean square, rather than the one point that seems warranted based
          on the rules outlined on page 36. Which is correct? I emailed Ravi Mohan
          about that, but never received a response.


        • Chuck Wolber
          ... I interpreted the question a bit differently. I saw no indication that the performance award of one point for being on a clean square would go away. The
          Message 4 of 5 , Oct 12, 2007
          • 0 Attachment
            On Tue, 2 Oct 2007, Abhijeet Sinha wrote:

            > Now in the next description, it is proposed that the vacuum-cleaner
            > agent would be wasting energy if it is allowed to move to the other
            > square if both the squares are clean. So very rightly the performance
            > measure deducts one point for moving into a clean square.

            I interpreted the question a bit differently. I saw no indication that the
            performance award of one point for being on a clean square would go away.
            The phrase "if the performance measure includes a penalty of one point for
            each movement" seems to indicate that this change is "included" with the
            previously stated performance measure of "one point for each clean square
            at each time step".

            This would mean that the agent would be awarded a point for being on a
            clean square and then lose it when it wastes energy going to another clean
            square. The performance measure score would always be zero.


            > So having one more assumption makes out earlier agent ir-rational.

            I concur because the spirit of the question seems to indicate that the
            penalty performance measure does not work in tandem with the original
            performance measure. I hope the wording can be reconsidered in the third
            edition.

            Just for fun... based on my reasoning above, wouldn't you agree that since
            the score would always be zero no matter what, the agent would be
            rational? Clearly it would have maximized its score.

            ..Chuck..
          Your message has been successfully submitted and would be delivered to recipients shortly.