Author: Dave Gomboc
Date: 23:00:35 11/29/99
Go up one level in this thread
On November 29, 1999 at 15:11:39, Robert Hyatt wrote: >On November 29, 1999 at 03:02:23, Paulo Soares wrote: > >>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 >> >>I agree with you, this is a valid sacrifice. >> >>Rebel Century(note that anti-GM=stronger)- PIII-450 >> >>First Position: >> >> +---+---+---+---+---+---+---+---+ >>8 | *R| | | | *Q| | *K| | >> +---+---+---+---+---+---+---+---+ 00:00:00 00:00:00 >>7 | *p| *p| *p| | *R| *p| *p| | >> +---+---+---+---+---+---+---+---+ >>6 | | | *N| | *B| | | *p| Time infinite >> +---+---+---+---+---+---+---+---+ Hash 60 Mb >>5 | | | | | | | | | Engine Rebel Century >> +---+---+---+---+---+---+---+---+ Personality Rebel Century >>4 | | | p | | | B | | | anti-GM Strong >> +---+---+---+---+---+---+---+---+ System Tiger Off >>3 | | | | B | | | | | Combination Off >> +---+---+---+---+---+---+---+---+ Style Normal >>2 | p | p | p | Q | | R | p | p | Strength Strongest >> +---+---+---+---+---+---+---+---+ Search Normal Search >>1 | | | | | | R | K | | >> +---+---+---+---+---+---+---+---+ >> a b c d e f g h >> >>r3q1k1/ppp1rpp1/2n1b2p/8/2P2B2/3B4/PPPQ1RPP/5RK1 w - - >> >>[Event "?"] >>[Site "?"] >>[Date "??.??.????"] >>[Round "?"] >>[White "Peter3"] >>[Black ""] >>[Result "*"] >>[WhiteElo "?"] >>[BlackElo "?"] >>[FEN "r3q1k1/ppp1rpp1/2n1b2p/8/2P2B2/3B4/PPPQ1RPP/5RK1 w - - 0 1"] >> >>1.* >> >>00:00:00 1.00 1.02 1.Bxh6 gxh6 2.Qxh6 > > > >This looks _incredibly_ dangerous. For every position where Bxh6 works, >there are 10 positions where Bxh6 loses. Here a piece for two pawns looks >awful if the other pieces can't get over to help out... Speculative play is >nice, as in the old days of the Novag gadgets from Kittinger, and in the current >play of CSTal... but it can backfire big-time as well... Whaaat?!? For humans, Bxh6 is the only move to even _look_ at here. I mean, all of white's pieces are pointing over there, and Black will consolidate if they're given the time to. In a blitz game, Bxh6 gets played instantly. In a longer game, you work it out, and if it doesn't work, you immediately jump to Rf3 and try to make Bxh6 work next move! If White isn't going to attack the kingside here, White's just worse, period. >Crafty doesn't like the sac, unless it sees actual material coming back, because >I have spent a lot of time teaching it which types of material imbalance are >bad and which types are good. A piece for 2 pawns is always bad unless there >is some tactical conclusion at the end. And given the above PV there obviously >isn't anything except a somewhat naked king position for black... "Somewhat naked"? It would be a miracle if Black could survive an attack on that king by the three heavies and the bishop in such good shape that White's attack would be unsound. The main question is: does the sac win outright, or can Black return material to defend? Dave
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