Author: Uri Blass
Date: 08:57:22 04/08/03
Go up one level in this thread
On April 08, 2003 at 11:30:55, Robert Hyatt wrote: >On April 08, 2003 at 11:16:24, Uri Blass wrote: > >>On April 08, 2003 at 10:57:21, Richard Pijl wrote: >> >>>On April 08, 2003 at 10:04:02, Uri Blass wrote: >>> >>>>[D]8/5pp1/4p1kp/1Q6/2rqP2P/8/5PP1/5RK1 w - - 0 27 >>>> >>>>This position happened in a game of movei. >>>>For the game see http://f11.parsimony.net/forum16635/messages/46511.htm >>>> >>>>I found that latest movei also suffers from the same evaluation problem. >>>> >>>>Movei evaluates the position as almost equal. >>>> >>>>I found that Crafty and a lot of programs understand that black has a clear >>>>advantage(more than 0.5 pawns for black from the >>>>first iterations). >>>> >>>>I understand that black is better but the question is what factor in evaluation >>>>helps a lot of programs to understand it. >>>> >>>>I can explain reasons to give advantage for black from program point of view: >>>> >>>>1)The black king is more advanced and it is known that the king should >>>>be at the last rank except endgames. >>> >>>I don't agree. After h5+ the black king is locked out from the immediate action >>>and has to retreat to h7. >> >>I understand it but piece square table gives h7 worse score >>than g1 for the king except endgames. > >Yes, but the piece square table (in crafty anyway) is a _small_ part of the >score for >a pawn or piece. It is really intended to be a "tie-breaker" and nothing else, >so that if >all else is equal (it rarely is) then the best piece-square value will break the >tie. It is also a small score for movei but it has no big scores for black here. > > >> >>I did not ask for opinion of humans but how do programs know it. >> >> >>> >>>>2)The white pawns are more advanced so by piece square table they >>>>get bigger bonus after a move like h5+. >>> >>>But that would increase the white score? >> >>Yes >>Piece square table give bigger score for the side that >>it's pawns are more advanced. > >Same comment again. Piece/square table values in Crafty are nothing but >tie-breakers. >The main positional scores are based on lots of other considerations, with the >pc/sq values >breaking a tie when two different positions seem to have the same non-pc/sq >scores. > >> >>> >>>I think you can detect black's advantage with three eval terms: >>>- Limited mobility of the white rook. It cannot leave square f1 because of >>>immediate threats on f2. >> >>I understand it but the question is if program understand it. >>Moei use number of moves to evaluate mobility and f1 is only slightly worse >>than possible sqares of the black rook. > >Then something is wrong with the way you are counting mobility. Mobility >along the first rank is _far_ less important than mobility along an open file, >or >along your opponent's 2nd rank (your 7th rank). If you are just counting >squares you >can move to, that is probably the problem. I don't do mobility for all pieces, >as there >are other terms that produce similar effects. IE rook on an open file means a >rook has >mobility along that file, for example. I do not do rook on an open file and movei knows to put rook in an open file thanks to mobility reasons. I know that my mobility evaluation can be improved but I am sure that it is clearly better than not doing mobility. > > > > > >> >>>- Black has two attacking pieces, White only one. >> >>Movei does not count attackers and I do not know if this is an important factor. > >Two pieces attacking squares around the king, being close to the king, is an >important factor. three pieces is even more important. This is a >"second-order" >evaluation term that has to factor in interrelationships among the pieces. I have small scores for attacking squares near the king but I do not count attackers. > > >> >>I think that the important factor is weaknesses of the white pawns. > >The score was not a pawn structure issue, as the score output showed. Pawn >structure is in the "pawn evaluation" line which was +.06 (good for white but >just barely). I understand but when I look at the game the problem was that movei was unable to defend it's pawns. I agree that it is impossible to say based only on the position of the pawns that the pawn structure is a weakness but I think that with different pawn structure that was demonstrated in the second diagram white has no problems in similiar conditions. Uri
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