Author: Gerd Isenberg
Date: 14:43:24 09/08/02
Go up one level in this thread
On September 08, 2002 at 15:41:50, martin fierz wrote: >On September 07, 2002 at 19:46:49, Peter McKenzie wrote: > >>I've been having a break from computer chess post WCCC, but have now started >>going over some of Warp's games. First up is Warp's worst game, the loss vs >>Brutus. In this game, Warp showed a total lack of understanding of its >>centralised king in the early middlegame and lost without a fight. >> >>I present here the position after move 21 in the game. White has grabbed a pawn >>thinking this position is OK, but in reality the white king is hopelessly stuck >>in the centre. Also, white is passive, black is active and has a safe king, >>therefore white is totally winning here: >> >>[D]r1r3k1/1p3ppp/b5q1/p7/4n3/P3PNB1/1P3PPP/1Q1RK2R b K - 0 1 >> >>I am curious what the static evaluation of various programs is here. The >>version of warp used in Maastricht gives 0.238 in favour of white. Ideally the >>static evaluation should favour black here I think. >> >>cheers, >>Peter > >the only important thing to recognize is that >Ba6 prevents castling && lots of material (queens!) on board. most important? > >i think you can easily give this kind of feature a value of 1 pawn. >however, you have to be kind of certain that it is here to stay. which >means that you should make sure that there is no move like c2-c4 before >applying this kind of rule. gerd gave a nice description of what his eval >is doing here, but i think part of it is no good: his count of "There are four >black pieces controlling squares with distance two from king." is probably no >useful measure. e.g. place the black bishop on b6 instead of a6, and you still >have that feature, but now it is black who has to hope for a draw. The order of the statements was rather random and doesn't imply any importance or weights. The most important is the (long time) lack of doing a castle or a indirect castle via Kf2,Re1,Kg1. That in conjunction with the rather missing ability to move a pawn or light piece to the diagonal. "There are four black pieces controlling squares with distance two from king" is a light weight, but is simply a heuristic that may improve the probability of "correctness". > >i know what you are worried about when not giving the "Ba6-prevents-castling & >queens on board" feature a higher eval. it might go away again, if white could >play something like Be2 or Ne2 and then castle. i have often thought about >similar things in my checkers program. in the end, i usually put high eval terms >for this kind of feature in anyway, because i think that if white can free >himself from this type of bind, the search will find it. however, if he cannot, >then it is very important that the eval tells you that he is in trouble. of >course i can search much deeper in checkers, which helps me believe that the >search will find it... > yes, but sometimes it's a decisive leaf-position :-) cheers, Gerd >aloha > martin
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