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Subject: Re: Search instabilities when re-using hashtables

Author: Robert Hyatt

Date: 20:23:41 06/21/02

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On June 21, 2002 at 23:05:25, Filip Tvrzsky wrote:

>Let me suppose my solution of your problems with hashed matescores (quite simple
>and in fact identical with that of Mr. Hyatt): adjust the evaluation every time
>just after you become it from the depth "depthroot + 1".
>Something like:
>        int Evaluation = -Alfabeta(-Beta, -Alfa, Horisont_alfabeta - 1);
>        if (Evaluation < -MATVALUE + 100) Evaluation++;
>        else if (Evaluation > MATVALUE - 100) Evaluation--;
>Of course, when the side to move is mated, you should return evaluation
>"-MATVALUE".
>And that is all! Then you do not need care for it more when hashing or using
>hash values. I use this solution in my chess program now (I had also big
>problems this kind for a long time) and it works fine!
>Sorry for my poor English.
>Filip Tvrzsky


That looks problematic.  alpha/beta values will be wrong, if I understand
what you are saying correctly.  That ought to make the search wildly unstable
in a position with _lots_ of mates in various numbers of moves.



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