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

Author: Ernst A. Heinz

Date: 02:00:14 11/18/98

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On November 17, 1998 at 06:36:49, Ernst A. Heinz wrote:

>On November 16, 1998 at 18:19:53, Amir Ban 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 move 36 but the other details are correct.
>>
>>The first time this was discussed on CCC, Chris Whittington was still here, and
>>he reported for CSTal. It was closer than others, but still couldn't bridge the
>>gap.
>
>I fed this position into the current "DarkThought" yesterday and it liked Qb6
>with a score of roughly +1.7 up to iteration #18 inclusively. Then, it failed
>low on Qb6 (score <= 1.39) in iteration #19 after processing 6,490,725,565
>nodes. Currently, it is still engaged in resolving the fail-low (see below).
>
>////////////////////////////////////////////////////////////////////////////////
>
>r1r1q1k1/6p1/p2b1p1p/1p1PpP2/PPp5/2P4P/R1B2QP1/R5K1 w - - 0 1
>
># Clearing chess engine.
># Engine sleeps.
>- -
>  +------------------------+
>8 |*R :::*R :::*Q :::*K :::|
>7 |:::   :::   :::   *P:   |
>6 |*P :::   *B:   *P:   *P:|
>5 |:::*P ::: P *P: P :::   |
>4 | P :P:*P :::   :::   :::|
>3 |:::   :P:   :::   ::: P |
>2 | R ::: B :::   :Q: P :::|
>1 |:R:   :::   :::   :K:   |
>  +------------------------+
>    a  b  c  d  e  f  g  h
>
>14.01  Qb6 Rd8 Be4 Rac8 Qxa6 bxa4 Qxa4 Qxa4 Rxa4 Rd7 ... (1.71) #62711053
>15.01  Qb6 Rd8 Be4 Rac8 Qxa6 bxa4 Qxa4 Qh5 Kh2 Qg5 ...   (1.69) #140398448
>16.01  Qb6 Rd8 Be4 Rac8 Qxa6 bxa4 Qxa4 Qh5 Qa7 ...       (1.70) #423411650
>17.01  Qb6 Rd8 Be4 Rac8 Qxa6 bxa4 Qxa4 Qh5 Qa7 Qh4 ...   (1.73) #1230726361
>18.01  Qb6 Rd8 Be4 a5 axb5 axb4 Rxa8 Rxa8 Rxa8 Qxa8 ...  (1.64) #3337837066
>19.01  Qb6 <=178? (1.39) #6490725565
>
>////////////////////////////////////////////////////////////////////////////////

I run this on a 500MHz Alpha-21164a and the fail-low of iteration #19 got
resolved to +1.26 after 14:34 hours and 11,196,023,081 nodes (see below).

>19.01? Qb6 Rd8 Be4 a5 axb5 axb4 Rxa8 Rxa8 Rxa8 Qxa8 ... (1.26) #11196023081

I will let "DarkThought" continue the calculation as long as the other people
at our institute do not get too angry at me for blocking so many Alphas ... :-)

=Ernst=



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