Author: Dan Homan
Date: 08:02:13 11/17/98
Go up one level in this thread
On November 16, 1998 at 21:07:53, Peter McKenzie wrote:
>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
EXchess gives
15. 1.17 8443 226739688 1. Qb6 Bf8 2. Qe6+ Qxe6 3. fxe6 Rab8 4. axb5 axb5
5. Bg6 Bd6 6. Ra7 Bc7 7. Kh1 Bb6 8. Rf7 Rc7
9. e7 e4
after completing the 15th iteration. This took 2 1/2 hours on a P133
equivalent machine. Deep Blue searched this many nodes in the first
second. :)
- Dan
P.S. EXchess briefly liked axb5 at ply 9, but Deep Blue likely completed
that iteration in the first half-millisecond or so (actually they do things
a bit differently in their search so maybe not so quick, but still well
within the first second).
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