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Subject: Re: DB vs Kasparov Game 2 35. axb5

Author: Peter McKenzie

Date: 18:07:53 11/16/98

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On November 16, 1998 at 14:50:57, Bruce Moreland wrote:

>r1r1q1k1/6p1/p2b1p1p/1p1PpP2/PPp5/2P4P/R1B2QP1/R5K1 w - - 0 1
>
>It has been contended that this move would be difficult for a computer to find,
>and this has caused some doubts to be raised as to whether the computer found it
>without assistance in this game.
>
>I would like to ask how we can clear this up absent input from DB.
>
>Has anybody run this for a long period on a micro, and if so, was any move
>selected other than 35. Qb6?
>
>Is the counter-attacking line 35. Qb6 Qe7 36. axb5 Rab8 37. Qxa6 e4 supposedly
>the reason that white shouldn't play 35. Qb6?  Or is it some other line?  If it
>is too hard or impossible to find 35. axb5, would finding this line show
>anything?
>
>Is there some minimum score delta we can achieve between the position after 35.
>axb5 and 35. Qb6 that might be evidence that DB should be given the benefit of
>the doubt?
>
>Are these questions unfair or wrong, if so, are their other questions that can
>be asked and possibly answered that will help clear this up?
>
>bruce

This is an excellent post.
I am interested in trying to find out an accurate evaluation of this position,
it should be possible I think.

Maybe DB saw very deeply and found something wrong with Qb6, or maybe Qb6 was
rejected due to a bug or an inaccurate king safety term.  Maybe DB just saw that
axb5 was even better than Qb6?  Any of these scenarios seem plausable.

First up, I ran the position on lambChop 6.90 for 1hr on a PII 266:

1. Qb6
Found in: 0sec, 4.21ply   Completed: 13.0ply
Used: 3600sec, Total Nodes: 109033472,  NPS: 30287
PV: Qb6 Bc7 Qe6+ Qxe6 fxe6 Rab8 axb5 axb5 Bg6 Bd6 Ra7 Bc7 Kh1
White by 1.3

I plan to look at it more closely this evening, would be interested in other
results.

Peter



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