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Subject: Re: Trouble with draw detection

Author: Pat King

Date: 07:29:41 03/22/04

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On March 21, 2004 at 15:21:22, Harald Lüßen wrote:

> Sometimes I see lines like this in
>the output:
>          14    248   3201     640337 Kf1-e2 Ra1-a2 Ke2-f1 Ra2-a1 Kf1-e2 Ra1-a2
>Ke2-f1 Ra2-a1 Kf1-e2 Ra1-a2 Ke2-f1 Ra2-a1 Kf1-e2 Ra1-a2 Ke2-f1 Ra2-a1 Kf1-e2
>Ra1-a2 Ke2-f1 Ra2-a1
>with score 248 instead of 0. May be there is an off by one error
>or the score finds a secret way out of the search algorithms. :-(
>The correct search would see the 0 instead of 248, avoid it and
>find a move with score 123 or whatever.

In Zotron I have a "Locked" field in the hash record, which is set by my search
routine when it first fetches a hash record, and released when the search
routine returns. If, further down the call stack, that record is encountered
again, I immediately return, thus short circuiting variations like the one
above.

Interestingly, it seems to work better if I return a qsearch score than a draw
score. Actual 3 times repetition is handled seperately with a "Reps" field in
the hash table.

>
>If you find a solution or anybody else knows it, please let me know.
>Is there an easy test position where this must happen?
>
>Harald

Hope this is useful.

Pat



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