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Subject: Re: Hashing and draw by repetition

Author: Robert Hyatt

Date: 07:28:59 08/26/99

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On August 26, 1999 at 03:23:43, Inmann Werner wrote:

>Hello
>
>When I began to implement hashing, I tried to use all "tricks" to avoid draws
>by repetition going into the hash tables, because I thought, this would be very
>bad.
>Yesterday I disabled this code and let also the draw by repetition evals into
>the hash tables, and surprisingly, the program worked better (at the complete
>LCTII Test)
>
>Do you also let "draw by repetition evals" into your hash tables?
>
>Werner


There is one serious error associated with hashing:  lack of path information.
Storing draws is not bad.  I have _always_ done this.  Others (David Slate,
for example) chose to not put draws into the hash.  However, I don't believe
that doing so causes any problems, even though it has some problems.  One
issue is that you search and find a draw and store the score.  Is there another
way to reach that same position where it isn't a draw?  yes...  and your hash
probe will be wrong.  I see no solution.

however, if you don't store draws, your problems are not over.  Because when
you search to P and store a good (non-draw score), and later search and reach
P via a different pathway, is the score still good?  Or is it possible that
between P and the endpoing where you did the eval, that you will now find a
repetition?  No way to answer that so you can _still_ get errors.

I ignore it...



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