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Subject: Re: Bruce Moreland - Examples, please :)

Author: David Rasmussen

Date: 10:00:19 01/16/03

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On January 16, 2003 at 12:40:47, Bruce Moreland wrote:

>
>It can't be done with a standard test suite, because it's a test "situation",
>not a test "position".
>

I was not asking for a test suite.

>The example with the knight fork is perfect.  I described something similar
>without providing a diagram.
>

I understood your example, but I still think it is possible to design a position
that will demonstrate the problem, if one does the right thing.

What happens in what you describe, is that we mix knowledge that is supposed to
be "perfect" (that is, search knowledge, we assumbe that both players will
always make the "best" move), and imperfect knowledge, the positions on the
board. If the opponent has made an error, he didn't choose the best move from
the position, so the logic breaks down. The position in which the error
happened, is regarded as a draw if encountered again, because what it is assumed
that what was moved the last time, was the best. This assumption doesn't hold
when the opponent has made an error.

>The problem with ignoring positions that are "one in the tree, one in the
>history", is that the program tends to diddle around, because it can make 2x
>reps without suffering a penalty.
>
>I didn't provide any examples of a program diddling around.
>

Provided with a position such as the one I described above, one could enter some
moves into the engine, so these moves were "over the board". One of these moves
should be an error. Then one could enter some more moves until reaching a
position where the program doesn't feel too good, but where it can choose to go
back to the position in which the erroneous move was entered. With one kind of
implementation, the program will choose to go back to that position because it
thinks it is a draw. With another implementation, it would choose something else
because it realizes that it isn't a draw yet, and that there is a much better
move in that position for the opponent, that would make the position even worse
for the program.

/David



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