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Subject: Re: Why can't any programs see this simple Bxh7 sac?

Author: John Stanback

Date: 20:58:53 06/14/99

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On June 14, 1999 at 14:14:21, Jeff Anderson wrote:

>Even most beginners learn to recognize when to play the Bxh7 sac, but for some
>reason not one of my engines, commercial or freeware considers it in the
>position below.  Even if the win is beyond its horizon, shouldn't most programs
>use tecniques to analyse lines like these deeper (extensions I think they are
>called.)  This theme so common, wouldn't it perhaps even be in the programs
>interest to recognize positions where it could work so they can play it, and not
>fall victim to it?
>Here is such a position where my expensive programs fail to even consider the
>move.
>
>r1b2rk1/3pqppp/p1nNp3/3nP3/5P2/1N1B4/1PPBQ1PP/5RK1 w - - 0 18

I was sort of surprised that Zarkov finds Bxh7 in
2 minutes, 40 seconds on a K6-333.  The score isn't all
that high though so it's probably a king safety heuristic
that's helping.  Here's the output:

00:01.0    35456  5>   -17  c4 Nc7 Qe4 Qh4 Nc5
00:02.0    84157  6>   -17  c4 Nc7 Qe4 Qh4 Nc5
00:02.3   103168  6    -40  c4 Nc7 Qe4 Qh4 g3 Qh6
00:02.6   115584  6    -22  Nxc8 Raxc8 Bxa6 Ra8 Bc4 Ndb4 Be3
00:07.0   364630  7>   -22  Nxc8 Raxc8 Bxa6 Ra8 Bc4 Ndb4 Be3
00:07.7   410496  7    -23  Nxc8 Rfxc8 Bxa6 Rcb8 Bc4 Nc7 Qd3
00:23.2  1324777  8>   -23  Nxc8 Rfxc8 Bxa6 Rcb8 Bc4 Nc7 Qd3
00:24.7  1429120  8    -30  Nxc8 Rfxc8 Bxa6 Rcb8 Bc4 Ra2 Bxd5 exd5 Bc3
00:29.4  1703296  8    -26  c4 Nc7 Qe4 g6 Nd4 Rb8 Bc3 Nxd4 Bxd4
00:58.2  3350016  8    -18  Be4 f6 c4 Nc7 Na5 fxe5 Qd3 h6 Nxc6 dxc6 fxe5
01:12.7  4216995  9>   -18  Be4 f6 c4 Nc7 Na5 fxe5 Qd3 h6 Nxc6 dxc6 fxe5
01:58.2  6579328  9     -4  Be4 f6 c4 Nc7 Na5 fxe5 Qd3 h6 Nxc6 dxc6 Bxc6
02:40.6  8674844  9     34  Bxh7+ Kxh7 Qh5+ Kg8 Rf3 g6 Qh6 Qxd6 exd6 Rb8 Na5
03:05.4  9838080  9     52  Bxh7+ Kxh7 Qh5+ Kg8 Rf3 Nf6 exf6 Qxf6 Rh3 Qh6
03:28.6 11108858 10>    52  Bxh7+ Kxh7 Qh5+ Kg8 Rf3 Nf6 exf6 Qxf6 Rh3 Qh6


John



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