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Subject: Re: Howard's positional sacrifice test

Author: Robert Hyatt

Date: 10:55:47 12/02/99

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On December 02, 1999 at 05:12:19, Ed Schröder wrote:

>>rnbq1rk1/p3nppp/1p2p3/2ppP3/3P4/P1PB1N2/2P2PPP/R1BQK2R w KQ - bm Bxh7+;
>
>Aha, a standard Bxh7+ case, it made the Novag Constellation world famous :)
>
>Another nice positional sacrifice later proven right by search. On ply 5 Rebel
>sacs the bishop in return for a strong king attack, no material gain is involved
>sofar, see Rebel's main-line. On ply 7 the sac is proven right as the score goes
>up to 2.15.
>
>Bob, sofar Rebel's king safety is doing well, no errors seen yet :)
>
>Please recover soon BTW.


I am home and doing ok...

My only concern was your Bxh6 after 1 ply only getting 2 pawns for the
bishop.  As I said, when I see that kind of behavior I find that Crafty
will find ways to make it happen deep enough in the search that the search
can't refute it...

Very ugly problem...

A very good test would be to get yourself on ICC and see how it does against
GM players.  It will catch them off-guard at first, but then they begin to watch
what is going on and they can see through the tricks once they notice that the
sacs are not always 'sound'...

I've had a lot of fun doing that kind of stuff...  But then I have taken a
lot of lumps, because rather than playing one game and being done, a GM will
play 30, and coax you into positions where you do this wrongly, if he can...




>
>00:00:00  4.00  0.34   1.Ng5 g6 2.O-O c4 3.Be2 h6 4.Nf3
>00:00:00  5.00  0.40   1.Ng5 g6 2.O-O c4 3.Be2 Ba6
>00:00:01  5.26  0.40   1.Bxh7+
>00:00:01  5.26  0.63   1.Bxh7+ Kxh7 2.Ng5+ Kg6 3.h4 Qe8
>                       4.Qg4  (1)
>
>00:00:01  6.00  0.72   1.Bxh7+ Kxh7 2.Ng5+ Kg6 3.h4 Qe8
>                       4.Qd3+ f5 5.h5+ Kh6 6.Nxe6+ Kh7
>                       7.Nxf8+ Qxf8  (1)
>
>00:00:03  7.00  2.15   1.Bxh7+ Kxh7 2.Ng5+ Kg8 3.Qh5 Re8
>                       4.Qh7+ Kf8 5.Qh8+ Ng8 6.Nh7+ Ke7
>                       7.Bg5+ Nf6 8.exf6+ Kd7 9.Qxg7  (1)
>
>00:00:05  8.00  2.57   1.Bxh7+ Kxh7 2.Ng5+ Kg6 3.h4 Qe8
>                       4.Qg4 Nf5 5.Nxe6+ Kh7 6.Qxf5+ Kg8  (3)
>
>00:00:49  9.00  2.22   1.Bxh7+ Kxh7 2.Ng5+ Kg6 3.h4 Qe8
>                       4.Qg4 Nf5 5.dxc5 bxc5 6.Nxe6+ Kh7
>                       7.Qxf5+ Kh8 8.exf6+  (10)
>
>
>>3r3k/p1b3p1/2R1pr1p/3q4/3PQ3/5p2/P4PPP/B3R1K1 b - - bm Bxh2+;
>
>No positional sacrifice here. Bxh2+ is found by normal search at ply 7.
>
>00:00:04  7.00  0.04   1..Bd6 2.Qxd5 exd5 3.g3 Rb8 4.Bc3
>                       Kh7 5.Ba5  (3)
>
>00:00:09  7.16  0.04   1..Bxh2+
>00:00:18  7.16  1.60   1..Bxh2+ 2.Kxh2 Qh5+ 3.Kg1 fxg2
>                       4.Kxg2 Rg6 5.Kf1 Rg4 6.Qf3 Rg1+
>                       7.Kxg1 Qxf3 8.Rcxe6  (9)
>
>Thanks John for the positions. It allows me to waterproof an important part
>of my chess program. I will try to extract some positional sacrifices from
>my own databases and post them.
>
>Ed



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