Author: Ricardo Gibert
Date: 12:26:43 08/05/99
Go up one level in this thread
On August 05, 1999 at 15:25:12, Ricardo Gibert wrote: >On August 05, 1999 at 10:40:16, Robert Hyatt 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. >> >> >>Again I refer you to Larry's article. In GM vs GM, RPP vs BN was drawn >>mostly. BN vs RP was won, mostly, by the BN side. That's all the data I >>have to go on... I'll try to find his article and provide the exact >>statistics he presented for these... >> >Nunn produced statistics that rook pawn + rook vs rook had about the same >winning percentage as center pawn + rook vs rook according to the KRPKR EGTB, >but everyone realizes this is a distortion. You know perfectly well that >statistics derived from games is even less scientific. It does not include >positions being avoid in analysis by the players. If your program does not avoid >these in its analysis, it can find itself in trouble. > >> >> >> >>> >>>> >>>>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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