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Subject: Re: Challenge position for engines! (Lots of luck)

Author: Andreas Stabel

Date: 00:50:04 03/07/02

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On March 05, 2002 at 08:12:17, Albert Silver wrote:

>On March 05, 2002 at 06:36:58, Ed Schröder wrote:
>
>>On March 05, 2002 at 05:15:38, Uri Blass wrote:
>>
>>>Yace also likes f5 and has Rh3 in the main line so it seems that finding a
>>>better move than Rh3 is not easy.
>>>
>>>The question is if Rh3 is winning.
>>
>>I don't know, a further investigation is needed IMO. Rebel gives a +2.30 score
>>for Rh3 after 15 plies but probably most of that is coming from eval.
>>
>>00:00:01.5	1,34	7	416116	Rh3 Kf7 exf5 Bxb3 Qxg6+ Ke7 Rh7+ Rf7
>>00:00:02.5	1,34	8	948561	Rh3 Kf7 exf5 Bxb3 Qxg6+ Ke7 Rh7+ Rf7
>>00:00:04.9	1,34	9	2379413	Rh3 Kf7 exf5 Bxb3 Qxg6+ Ke7 Rh7+ Rf7
>>00:00:08.7	2,22	10	5564762	Rh3 Kf7 exf5 Bxb3 Qxg6+ Ke7 Rh7+ Rf7
>>00:00:16.6	2,10	11	12107255	Rh3 Kf7 exf5 Bxb3 Qxg6+ Ke7 Qg5+ Rf6
>>00:00:42.6	1,78	12	31920754	Rh3 Kf7 Qh7+ Kf6 Qh4+ Kg7 Bxe6 Qxe6
>>00:02:02.0	1,62	13	95158047	Rh3 Kf7 Qh7+ Kf6 Qh4+ Kf7 exf5 Bxb3
>>00:06:49.0	2,30	14	322198950	Rh3 Kf7 Qh7+ Kf6 Qh4+ Kg7 Bxe6
>>00:14:38.6	2,30	15	688286326	Rh3 Kf7 Qh7+ Kf6 Qh4+ Kg7 Qh7+ Kf6
>>
>>
>>
>>>If Rh3 is not winning then it means that Rebel found the right move for the
>>>wrong reasons
>>
>>That's a popular statement in this forum, I once had similar thoughts but
>>changed my mind. It does not matter if Nxg6! is played by eval or search, the
>>only thing that matters is playing the good move.
>
>Yes and no. Suppose it finds Nxg6 but yields a draw score with a perpetual check
>in its main line. Nxg6 is a winning move, so if Rebel were to play it thinking
>it drew, how do you know it won't content itself with the draw? Would you
>consider it found Nxg6, the _winning_ move, just because it played it? That for
>me is the crucial question. I often see programs find a very delicate sacrifice
>but with a draw score, and even by feeding them the responses, they do not win
>the game. So what then?
>
>Uri's comment here is relevant also because it isn't shown why Rebel immediately
>sacs the bishop back with Bc1. No doubt this is the best reply for Black, but
>did Rebel do this because it saw a genuine follow-up for White if f5 was played,
>or did it see a ghost?
>
>As to the comment on Rh3, it wasn't so much a complaint (I saw the smiley BTW)
>as comment on my challenge: find the strongest continuation. In this case, let's
>broaden this to find the best continuation after 25.Nxg6 hxg6 26.Qh6 Be6 27.Rd3
>f5.
>
>The strongest continuation BTW isn't 28.Rh3, it is 28.Rg3! Rf6 29.Rh3 Kf7
>30.Qh7+ Kf8 31.exf5!
>
>                                          Albert

I let crafty run over night on the position after 28. Rg3:
18-> 946:29   0.46   4. ... Rf6 5. Rh3 Kf7 6. Qh7+ Kf8 7.
                     exf5 Bxb3 8. axb3 Rxf5 9. b4 Rh5 10.
                     Bc5+ Ne7 11. Rf3+ Rf5 12. Rxf5+ gxf5
                     13. Qxf5+ Qf7 14. Qxe5 Qh7 15. g4 Bb2
                     16. f4 Qb1+ 17. Kf2

It doesn't seem very convincing to me.

Best regards
Andreas Stabel



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