Author: Uri Blass
Date: 11:05:58 04/08/03
Go up one level in this thread
On April 08, 2003 at 13:24:33, Richard Pijl 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. >> >>I did not ask for opinion of humans but how do programs know it. >> > >I did not answer for myself, but how the Baron looks at it (shallow search score >of the latest development version is around 0.7 for black in the Baron too) > >In the endgame h7 is only marginally better than g8. And with a pawn attacking >one of the fields directly in front of the king, the score drops even more. > >> >>> >>>>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. >> >>> >>>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. > >1. Rook is bad on f1 as it has no free squares along the file >2. Shallow search discovers that the rook cannot leave f1 because of threats on >f2. > >You were talking about evaluation after a shallow search, so I took that into >account in the answer. > >> >>>- Black has two attacking pieces, White only one. >> >>Movei does not count attackers and I do not know if this is an important factor. > >Yes, it is important. A lone queen near the enemy king is only giving you some >sort of attacking possibilities when it is supported by another piece. >Proximity is another thing that should count, but is probably less relevant in >this position. > >> >>I think that the important factor is weaknesses of the white pawns. > >The pawns are weak, but it costs moves to capture them. Possibly a queen >exchange can be forced during the capture, which makes it really hard to win the >resulting endgame despite the extra pawn. > >Just remove the queens and the h4 or e4 pawn from the board. Can you still win >it? > >>Here is another position when I think that black >>has no advantage inspite of Crafty's opinion. >> >>[D]8/5pp1/6kp/1Q6/2rq4/7P/5PP1/5RK1 b - - 0 1 > >Baron thinks the black advantage is a little less (in shallow search) than in >the previous position. Winning this endgame is something different though which >is discovered in search: After 3 minutes the score dropped from 0.71 to 0.23 >(for black). > >Richard. I guess that the baron assumes that it is an endgame. I do not do this assumption. For me endgames are only positions when the king should be active. Queen and rook are dangerous material for mate attack and in general it is dangerous for the king to go to the centre of the board. Uri
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