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Subject: Re: null move question(Fruit)

Author: Johan Melin

Date: 12:01:21 07/23/04

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On July 22, 2004 at 20:50:14, Jan K. wrote:

>Hi, i have seen in fruit and in other engines too that there is no test if
>(remainingDepth-rFactor-1)>(=)0 before doing null move, only
>remainingDepth>=someConstant, which means making many cutoffs based only on the
>values given by qsearch. That gived a very nice speed up when I tried it, but I
>soon found that my engine makes mistakes in some positions like this one, where
>it shows a draw after <almost every move> <e6e2> <d3c4> <f7g6> <c4d3>, altough
>only <d3c4> doesn't lose(normally seen at depth 5):
>[D]8/5kpp/4rp2/2p5/PP1p4/3Q2PP/2P2q2/R1B4K w - - 3 30
>it didn't help when I used verification search, checks in qsearch....

Checks in qsearch should matter here. The critical variation ends with a
mate-threat and no good defense. If that threat is understood by qsearch, null
move will do ok, I think. But if it does not, null move will add several plies.

CV(-0.21): Ba3 Re2 Qc4 Kg6 Qd3? f5! Qa6 Kh5! g4? Kh4! none

/Johan Melin

>But Fruit doesn't seem to have a problem so do I have a bug or just miss
>something? :))

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