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Subject: Re: draw by repetition and hash tables

Author: Don Dailey

Date: 06:08:24 07/25/98

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On July 24, 1998 at 00:38:01, Inmann Werner wrote:

>Hello all!
>
>can anybody help???
>
>I have some problem to implement draw by repetition in my program.
>If a position is reached the third time, its a draw by repetition. Ok.
>But the position has an evaluation. But because of the draw I return zero
>(draw). Now all positions before in alpha beta get a Score of zero. OK.
>But this values also may come into the hashtables, and thats really bad and
>not correct!
>Does anybody have the same problem, and maybe solved it?
>
>Werner

There seems to be no general solution that does not slow the
program down significantly.  The problem is even worse than this
because draws by rep can affect the score of a position too.

In my program I just do not store draw scores.  I make those
scores unique by multiplying every score times two and making
the draw score the only ODD score.   This is NOT a perfect
solution but I do not know what else to do.

This has been talked about on this group many times though,
be sure and check out the older posts if you have the energy
to dig through them.

- Don








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