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Subject: Re: A case when Movei earn 2 plies from verified null move pruning

Author: Omid David Tabibi

Date: 16:55:23 11/22/02

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On November 22, 2002 at 19:43:10, Martin Giepmans wrote:

>On November 22, 2002 at 18:09:28, Uri Blass wrote:
>
>>previous version found Rxb2 only at depth 14
>>With verified null move pruning movei finds wac 2  at depth 12.
>>
>>[D]8/7p/5k2/5p2/p1p2P2/Pr1pPK2/1P1R3P/8 b - - 0 1
>>
>>depth=12 +0.64 b3b2
>>Nodes: 6559172 NPS: 215975
>>Time: 00:00:30.37
>>
>>depth=12 +2.67 b3b2 d2b2 c4c3 b2b6 f6g7 b6b7 g7h6 b7b6 h6h5 b6b5 c3c2 b5f5 h5g6
>>f5g5 g6h6 g5c5 d3d2 c5c6 h6h5 c6c5 h5h4 c5c2 d2d1q c2e2
>>Nodes: 17674291 NPS: 212303
>>Time: 00:01:23.25
>>
>>depth=13 +3.54 b3b2 d2b2 c4c3 b2b6 f6g7 b6b7 g7h6 b7b6 h6h5 b6b5 c3c2 b5f5 h5g6
>>f5g5 g6f6 g5c5 d3d2 c5c6 f6e7 c6c7 e7d6 c7c2 d2d1q c2e2 h7h5
>>Nodes: 30679118 NPS: 220032
>>Time: 00:02:19.43
>>
>>Uri
>
>I don't think that pure nullmove (without any verification) is safe
>in an endgame like this. So I'm not amazed that verified nullmove does better
>here.
>

I don't think the improvement comes from zugzwang detection here, since I can
see no zugzwang after Rxb2.

This can be checked by turning off zugzwang detection (the re-search part).


>Martin



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