Author: Robert Hyatt
Date: 07:42:09 08/05/99
Go up one level in this thread
On August 05, 1999 at 00:47:24, Ricardo Gibert wrote: >On August 05, 1999 at 00:44:35, Ricardo Gibert wrote: > >>On August 04, 1999 at 23:29:12, Robert Hyatt wrote: >> >>>On August 04, 1999 at 21:04:00, Ricardo Gibert wrote: >>> >>>>On August 04, 1999 at 20:08:41, Robert Hyatt wrote: >>>> >>>>>On August 04, 1999 at 17:32:51, Ricardo Gibert wrote: >>>>> >>>>>>On August 04, 1999 at 16:30:38, Robert Hyatt wrote: >>>>>> >>>>>>>On August 04, 1999 at 14:40:31, KarinsDad wrote: >>>>>>> >>>>>>>>On August 04, 1999 at 14:09:18, Bruce Moreland wrote: >>>>>>>> >>>>>>>>> >>>>>>>>>On August 04, 1999 at 12:16:52, Dann Corbit wrote: >>>>>>>>> >>>>>>>>>>As a 'for instance': >>>>>>>>>> >>>>>>>>>>Suppose that on promotion, a program sees that it can promote to a knight >>>>>>>>>>instead of a queen, and get a king fork, taking a bishop, followed by a queen >>>>>>>>>>fork, taking the other bishop. In such a case, it might evaluate: >>>>>>>>>> -pawn+knight+bishop+bishop+two_bishop_bonus+(minor positional goo) >>>>>>>>>>verses >>>>>>>>>> -pawn+queen >>>>>>>>>>and get something a fraction more valuable than a queen. But down the road I >>>>>>>>>>would rather have the queen than a knight and remove the two bishops. >>>>>>>>>> >>>>>>>>>>How do programs deal with this? >>>>>>>>> >>>>>>>>>You are really saying you'd rather have a queen against two bishops than be a >>>>>>>>>knight up, right? >>>>>>>>> >>>>>>>>>bruce >>>>>>>> >>>>>>>>Actually, assuming an equal game, it is a preference of being up a queen for a >>>>>>>>pawn as opposed to being up a knight and two bishops for a pawn. >>>>>>>> >>>>>>>>Of course, decisions like these are always based off of the actual position, but >>>>>>>>here is a comment Kasparov made just the other day on Ponomariov - Al Modiakhi >>>>>>>>in round 1 of the championship: >>>>>>>> >>>>>>>>"Looking at Ponomariov's 7.Be3 with 8.Bb6 I have sensed chess of the very >>>>>>>>distant future. With my limited knowledge of the game I would consider 3 minor >>>>>>>>pieces in such position much better than Queen+pawn". >>>>>>>> >>>>>>>>So, there are obviously positions where having 3 minors is better than having >>>>>>>>the queen. >>>>>>>> >>>>>>>>KarinsDad :) >>>>>>> >>>>>>> >>>>>>>I think that in almost _all_ cases, three minors pieces are better than a >>>>>>>single queen.. and most games I have seen where this happens are wins for the >>>>>>>three minors. I don't like two minors and 3 pawns vs a queen however, unless >>>>>>>maybe if the pawns are all on the 6th rank or farther along. :) >>>>>> >>>>>>I felt pretty sure about this too, but I analyzed with Jack Peters a particular >>>>>>position and came away with idea that it was a lot closer than I thought and >>>>>>that subjective factors have a big impact. I still prefer the 3 pieces, but now >>>>>>I am more careful. The 3 pieces don't organize themselves very quickly, but the >>>>>>Q is relatively much faster in this respect. It depends very much on the >>>>>>position. >>>>>> >>>>>>Related to this topic is R+P+P vs B+N. You have indicated that you set this as >>>>>>equal. At first I thought this was a mistake, but then I thought about it and >>>>>>this may be right for chess playing programs, since they are not sufficiently >>>>>>effective in getting the rook into play. As a human, I use R+P < B+N < R+P+P. I >>>>>>believe this is the "normal" evaluation. R+P+P = B+N is a practical choice for >>>>>>computers. Of course subjective factors must be considered. >>>>> >>>>> >>>>>I have done that for a long time... but IM Larry Kaufman published an article >>>>>in Chess Life (not about computers particularly) about such material >>>>>imbalancess, and he concluded after looking at a lot of games, that two pieces >>>>>are about equal to R+P+P. Of course, if the two pawns are on the 7th, that >>>>>goes out the door, naturally... or if they are connected passers that can roll >>>>>quicker than the two pieces + the king can mobilize to win them... >>>> >>>>That is what he may have said, but he is going against the opinion of a lot of >>>>strong players all the same. In the endgame for example, Reuben fine states that >>>>R+P vs 2 minors is a draw, with more pawns on both sides it is still normally >>>>drawn, while R+P+P vs 2 minors always win. His use of "always" pre-supposes a >>>>"normal" position. >>>> >>>>It's true, before the endgame, comes the middlegame, so the side with 2 minors >>>>MUST play very energetically to avoid loss. The side with the 2 minors is in >>>>trouble. It is very possible to get compensation, since it is often not so easy >>>>to activate the rook in the middle game. >>>> >>>>You should change your eval for the endgame at least. >>> >>> >>>I think this is just another case where Fine is wrong. Larry's results were >>>based on studying games between top players, and looking at games with a >>>specific material imbalance, and then determining the win/lose/draw ratio for >>>each side. He concluded, based on actual GM play, that two minors vs a rook and >>>pawn is a significant advantage... and that this advantage holds until it >>>becomes a rook and two pawns vs the minor, then it becomes 'equal'. >> >>That R+P+P has an advantage over B+N is undeniable. > >In the endgame of course. >> the problem is that such positions first arise in the middlegame. But even in an endgame, it is not terribly hard to sacrifice one piece for the two pawns since that side can attack a square one more time than the opponent can. And KR vs KB or KR vs KN is a draw. >>> >>>Again, based on previous games GM vs GM without computers in the loop... That >>>wasn't really news as most everyone considers B+N vs R+P to be bad for the R+P >>>side (which is why such trades on f2/f7 are not played very often in high-level >>>chess games.) He found other interesting things as well and published them in >>>his article in CL.
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