Author: Ross Boyd
Date: 12:30:03 01/18/06
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On January 18, 2006 at 15:05:36, Dann Corbit wrote: >On January 18, 2006 at 14:39:40, Fernando Villegas wrote: > >>Some days ago I talked of knowledege to know which knowledge is irrelevant as a >>probable feature of Rybka. And almost nobody answered or commented my post. >>Surely it is an advantage to be a chess programmer in a site like this. > >Probably the only one who can answer correctly is the author. > >But you can look at some interesting generalizations. > >I have found that some evaluation terms add nothing either to the EPD solution >count or the contest point gathering effectiveness of an engine. > >An example is queen mobility. I don't know of any logical reason why its >computation should not help, but it doesn't. > >I have seen other chess engine authors come to the same conclusion. Agreed. I do pseudo mobility only for bishops and knights. Queen mobility improves nothing. However, I do piece-square so the queen knows about centralisation. > >So there can be a case where you add this wonderful knowledge term that makes >your engine smarter and have better chess insight. But when you compute it and >add it in to the overall score, the net effect is nothing except to slow the >engine down. If you do add knowledge it has to be relevant, non-redundant and preferably augments the search. Mobility is a good eval function because of its general usefulness in 95% of positions. Good candidates for chess knowledge are terms that effectively increase the depth of the search... eg recognition of bad bishop and rook pawn draws. Search alone is not enough since a good static eval can detect this situation many plies earlier. Ross
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