Author: John Stanback
Date: 16:55:31 11/29/99
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On November 29, 1999 at 00:32:17, Peter McKenzie wrote: >The following position is from a blitz game between Hossa and Beadle (LambChop) >on ICC: > >r3q1k1/ppp1rpp1/2n1b2p/8/2P2B2/3B4/PPPQ1RPP/5RK1 w - - > >Hossa played Bxh6 and wiped Beadle out. This position is an interesting test of >king safety evaluation, as there is no short range mate or win of material after >the sac although I'm pretty confident the sac is correct. > >I tried this position with LambChop, and it too liked Bxh6 giving it a score of >about +0.5 pawns from depths 4 thru 8. On depths 9-10 it switched to Qc3 with a >similar score of around +0.5, then at depth 11 it switched back to Bxh6 and the >score jumps to +1.4. Depth 12 is still Bxh6 at +1.6. > >We discussed this position a bit on ICC, Bob ran it on Crafty which didn't want >to play Bxh6. Peter Kappler ran it on Hiarcs which liked Bxh6 straight away >with a +1 score! Diep also liked Bxh6 from early on, and had an even higher >score. I wonder what Hiarcs and Diep are doing in eval that Crafty isn't... or >vice-versa. > >How about other programs? >What do the human chess experts think? > >If that position is too hard, it might be productive to play down the main line >of accepting the sacrifice. So after 1.Bxh6 gxh6 2.Qxh6 we have: > >r3q1k1/ppp1rp2/2n1b2Q/8/2P5/3B4/PPP2RPP/5RK1 b - - > >Here LambChop gets a score jump from -0.2 at ply 7 to -1.7 at ply 8. Not quite >sure why :-) > >cheers, >Peter Zarkov likes Bxh6 at all iterations. The score jumps to +1.67 pawns at iteration 8 but drops to +1.42 at the 9th. I have some pretty high king safety penalties. Sometimes they backfire, but mostly I think they're ok. Here's the output: 00:01.0 29440 5> 65 Bxh6 gxh6 Qxh6 f5 Bxf5 <HT> 00:01.0 29707 6> 65 Bxh6 gxh6 Qxh6 f5 Bxf5 <HT> 00:01.7 61696 6 74 Bxh6 gxh6 Qxh6 f5 Bxf5 Bxc4 Bg6 Qc8 Ra1 00:02.3 93063 7> 74 Bxh6 gxh6 Qxh6 f5 Bxf5 Bxc4 Bg6 Qc8 Ra1 00:04.3 204032 7 100 Bxh6 gxh6 Qxh6 f5 Bxf5 Bxc4 Rf4 Ne5 Rh4 00:06.7 330299 8> 100 Bxh6 gxh6 Qxh6 f5 Bxf5 Bxc4 Rf4 Ne5 Rh4 00:38.3 1763651 8 162 Bxh6 gxh6 Qxh6 f5 Bxf5 Bxc4 Rf4 Ne5 Rh4 Bxf1 Qh8+ 00:55.5 2471040 8 167 Bxh6 Ne5 Qg5 Ng6 Bxg6 fxg6 Rf8+ Qxf8 Rxf8+ Kxf8 00:58.2 2602786 9> 167 Bxh6 Ne5 Qg5 Ng6 Bxg6 fxg6 Rf8+ Qxf8 Rxf8+ Kxf8 02:47.1 7726848 9 142 Bxh6 f6 Bf4 Bf7 Re2 Rxe2 Bxe2 Rd8 Bd3 Ne5 02:55.3 8140386 10> 142 Bxh6 f6 Bf4 Bf7 Re2 Rxe2 Bxe2 Rd8 Bd3 Ne5 John
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