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Subject: Re: Disappointment as Fritz 5,6+Hiarcs fail to find this elegant move! WHY?

Author: John Stanback

Date: 19:44:13 05/09/00

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On May 09, 2000 at 20:08:10, Dann Corbit wrote:

>On May 09, 2000 at 20:05:02, John Stanback wrote:
>>On May 09, 2000 at 10:34:20, Mark Andreoli wrote:
>>>   I recently played a 5 minute blitz game against International Master Nenad
>>>Aleksic. see moves below: (I lost as I am black.)
>>>
>>>        1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 g6 6.Be3 Bg7 7.f3 O-O
>>>
>>>        8.Bc4 Nc6 9. Bb3 Bd7 10.g4 Qa5 11.h4 Rfc8 12.h5 Ne5 13.hxg6 hxg6
>>>
>>>        14.Bh6 Bh8 15.Qd2 b5 16.O-O-O Nc4 17.Bxc4 Rxc4 18.Nb3 Qc7 19.Bf8!! OK
>>>
>>>       "gang" the parties over. All variations are FORCED and win rather quickly
>>>        for white. The game continued 19. ...  Rxf8 20.Rxh8+ Kxh8 21.Qh6+ Kg8
>>>
>>>        22.Rh1 Nh5 22. gxh5 Rxc3 23.hxg6  1-0
>>>
>>>         My question is _why_ can't the above mentioned "engines" F5/F6/Hiarcs
>>>find the move 19. Bf8 (Nenad found it in only 20 seconds). The engines all want
>>>to play Bg5??
>>>
>>>           _which wins too_ in a __long endgame_ however I thought nothing could
>>>beat these chess computers when it came to tactics.
>>>       Maybe I overlooked something? Maybe Junior,Rebel,CM 7000 or Chess Tiger
>>>can find this "simple but elegant tactical shot"! Could anyone help me out by
>>>checking the position after the 18th move. I would love to be corrected and/or
>>>enlightened. Thanks for any help in solving this _mystery_!? MJA :-(
>>
>>Zarkov takes 2:52 on a K6-550:
>>
>>
>>00:01.0    38784  5>    68  g5 b4 Ne2 Nh5 Nbd4
>>00:01.1    39442  5    114  Bg5 b4 Bxf6 Bxf6 Nd5 Kg7
>>00:01.4    63104  5    141  Bg5 Bg7 Bxf6 Bxf6 Nd5 Qc6 Nxf6+ exf6
>>00:01.4    66204  6>   141  Bg5 Bg7 Bxf6 Bxf6 Nd5 Qc6 Nxf6+ exf6
>>00:01.8    93184  6    141  Bg5 Bg7 Bxf6 Bxf6 Nd5 Qc6 Nxf6+ exf6
>>00:02.1   114163  7>   141  Bg5 Bg7 Bxf6 Bxf6 Nd5 Qc6 Nxf6+ exf6
>>00:03.7   235904  7    166  Bg5 Bg7 Bxf6 exf6 Qxd6 Qxd6 Rxd6 Rc7
>>00:05.0   345626  8>   166  Bg5 Bg7 Bxf6 exf6 Qxd6 Qxd6 Rxd6 Rc7
>>00:09.4   717824  8    193  Bg5 Bg7 Bxf6 exf6 Qxd6 Qxd6 Rxd6 Be8 Nd5
>>00:10.5   812957  9>   193  Bg5 Bg7 Bxf6 exf6 Qxd6 Qxd6 Rxd6 Be8 Nd5
>>00:21.5  1658880  9    177  Bg5 Bg7 Bxf6 exf6 Qxd6 b4 Qxc7 Rxc7 Nd5 Rb7
>>02:52.3 12780800  9    193  Bf8 Rxf8 Rxh8+ Kxh8 Qh6+ Kg8 Rh1 Nh5 gxh5 Rxc3
>>02:53.7 12904562 10>   193  Bf8 Rxf8 Rxh8+ Kxh8 Qh6+ Kg8 Rh1 Nh5 gxh5 Rxc3
>
>Another amazing result.  Can you comment on how your program was able to find
>this by ply 9?

After investigating this, I find that Zarkov was quite lucky.
My current re-capture extensions are pretty heavy and allow it to
search one extra ply in the critical line.  Also, a "feature" (bug?)
in my one-reply check extension routine made it double-extend after
Qh6+ in the line below:
  Bf8 Rxf8 Rxh8+ Kxh8 Qh6+ Kg8 Rh1 Nh5 gxh5 Rxc3 hxg6 Rxc2+ Kb1 Rxb2+ KxR
even though black has two legal moves.

John




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