Author: Ricardo Gibert
Date: 17:48:39 11/30/99
Go up one level in this thread
On November 30, 1999 at 17:43:50, Robert Hyatt wrote: >On November 30, 1999 at 03:35:54, Ed Schröder wrote: > >>>Posted by Robert Hyatt on November 29, 1999 at 20:17:47: >> >>[ snip ] >> >>r3q1k1/ppp1rpp1/2n1b2p/8/2P2B2/3B4/PPPQ1RPP/5RK1 w - - bm Bxh6; >> >>>>>>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... >>> >>>>> >>>>>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... >>>> >>>>I can not believe you saying this. After 1.Bxh6 gxh6 2.Qxh6 there is a queen, >>>>2 rooks and a bishop all pointed very dangerous at a naked king. Rebel giving >>>>+1 is fully justified. >>>> >>>>Every 1800 rated chess player will play 1.Bxh6 immediately, no need to >>>>calculate. >>>> >>> >>>Sorry, but _I_ am an 1800+ player and _I_ wouldn't play it immediately. >>>Because black can play f5, and it doesn't look nearly so clear after that. The king >>>has a way out... the black rook now can interpose on the g/h files. The >>>f file is no longer useful unless white does something else... >> >>1.Bxh6 gxh6 2.Qxh6 f5 3.Bxf5 the black king is even more naked. I guess >>we have a different view on king safety. > > > >I probably have as big (or bigger) king safety scores as you. However, I >have a big penalty for trading a piece for 2-3 pawns, as it almost always >loses unless tactics make it work... > >> >>>It may be good. It may not work. But as a human, I don't play Bxh6 here >>>without calculating something worthwhile at the end of the sequence. I let >>>an IM look at this for several minutes... he left unclear whether it was >>>good or not... >> >>Who was the IM? >> >>After 1.Bxh6 gxh6 2.Qxh6 f5 3.Bxf5 I am pretty sure all programs soon will >>display a +2 or +3 score. > > >Note that I didn't say it doesn't work. I said that at the shallow depth >of 1-2-3-4 plies, it looks _very_ dangerous to do this.. because black has >some defensive resources that don't look obviously bad until you search >deeper. I think the culprit is crafty does not understand the role the passive rook on a8 has in assessing the position. The value of a passive major piece in such a sharp position plummets precipitously. After 3.Bxf5, any evaluation less than half a pawn in favor of white should be considered a bug. Naturally, the actual evaluation for white is much greater, but I assume here that the program does not "see" the win. You have said that crafty generally does not play such sacrifices, unless it "sees" a win, calling programs that do otherwise "speculative". But isn't crafty guilty of doing the reverse? It is speculating that the sac is unsound despite positional evidence to the contrary. Crafty trades one form of speculation for another at the cost of being boring. > >That was my point... that tossing a piece for 2 pawns, with no concrete idea >of whether it will work or not, seems dangerous. IE what if we move a couple >of black pieces, leaving white's pieces as is. It won't be too hard to (say) >move the second black rook so that it helps the other rook defend... and one >more black piece in the game and the attack doesn't work at all... > >Would you _still_ play the sac? That is the danger. I definitely would want >to play it in blitz. And I definitely wouldn't want to play it in a 40/2hr >game knowing that the GM has all the time in the world to find the refutation. > > > > >> >>Based on this I wouldn't call this position a 100% positional sacrifice as >>it is somewhere in the 10th ply area (depending on a programs extension >>use).\ > > >Somewhere around 3 minutes crafty fails high on Bxh6. So it probably does >work tactically based on that. But you liked it at ply=1, which was the thing >that seemed dangerous... because at ply-1 it is _definitely_ based on position >alone.. > > > > >> >>>That is what I meant by "this looks incredibly dangerous". Because if you >>>don't get something back from this, you are pretty well sunk. The position looks >>>pretty nice for white. But good enough to toss a piece immediately? Unclear >>>without a lot more analysis... >>> >>>to me >> >>As said we must have a different view on king safety even on the basics as >>this case for me is so crystal clear: QRRB all pointed at a naked king, the >>king having hardly any escapes, the black pieces not able to defend its >>own king. Based on that Rebel gives a 2 pawn positional bonus after >>2.Qxh6 and even more after 3.Bxf5. >> >>See also my points regarding this issue in another posting. >> >>Ed
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