Author: Ricardo Gibert
Date: 12:29:10 11/30/99
Go up one level in this thread
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 1.Bxh6 gxh6 2.Qxh6 f5 3.Bxf5 Three pawns for the piece, the passive a8 rook and the exposed Black K attest to the soundness of Bxh6. 3...Nd4 Not taking on f5 is tantamount to resignation, but on 3...Bxf5 4.Rxf5 Rg7(4...Re5 5.R5f3) 5.Rh5+- Rxg2+ 6.Kxg2 Qe2+ 7.Kg3 Qxf1 8.Rg5+ Kf7 9.Rg7+ Ke8 10.Qe6+ 4.Bg6 Also simple is 4.Bd3 Rg7 5.c3 (5.Rf4) 5...Nc6 6.Re2 or 6.Rf8+ winning 4...Qd8 5.Bd3 Workable, but more complex is 5.c3 Bxc4 (5...Nc6 6.Rf7 Rxf7 7.Rxf7 Qd1+ 8.Rf1) and now 6.cxd4? Qxd4 is unclear(6...Bxf1? 7.Rf4 wins), but 6.Rf6!+- Ne2+ (6...Bxf1 7.Bf7+; 6...Rg7 7.b3)7.Kh1 Rg7 8.b3. Not workable is 5.Rf7? losing to Ne2+ (But not 5...Rxf7? 6.Rxf7 Ne2+ 7.Kf2 Qd4+ 8.Ke1 Qg1+ 9.Rf1) 6.Kh1 (6.Kf2 Rxf7+ 7.Bxf7+ Bxf7 8.Kxe2 Bxc4+) 6...Rxf7 7.Bxf7+ Bxf7 5...Rg7 6.c3 or 6.Rf4 win.
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