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Subject: Re: draw recognition and hash interactions

Author: Rafael Andrist

Date: 05:51:32 07/19/01

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On July 19, 2001 at 06:34:53, Tony Werten wrote:

>On July 18, 2001 at 06:00:32, Rafael Andrist wrote:
>
>>My program missed to avoid a draw in a game (see below) due to some strange
>>interactions between search and hash. I investigated it and recognized the
>>following problem:
>>
>>- at move 33 my program recognizes a 2x and a 3x rep. during the search. The 2x
>>rep. is allowed and the 3x is avoided. But in the hash, the move leading to a 3x
>>rep. is stored.
>
>How is this different from the move leading to 2x rep ?
>
>Tony

I see, my explanation was a bit unclear. Inside the search, there's a difference
in the score stored with the move. But in the hash rests only the move without
the draw score. This isn't a problem during this search (at move 33), but it
causes problems in the next search (at move 35).

Rafael B. Andrist

>>- I get PV completly from hash, so the displayed PV is incorrect (shows 3x rep.)
>>but the real PV (inside the search) is correct
>>- at move 35 my porgram gets the PV leading to a 3x rep. from hash. The PV has a
>>length of 8 ply
>>
>>---> my program cannot search to 9 ply because it has not enough time (fixed
>>time per move), so it takes the move recommended from hash and draws.
>>



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