Author: Andrew Williams
Date: 08:36:25 10/27/99
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On October 27, 1999 at 11:07:43, Robert Hyatt wrote: >On October 27, 1999 at 06:25:31, Andrew Williams wrote: > >>On October 27, 1999 at 02:59:52, James Robertson wrote: >> >>>I'm trying to write some code to evaluate passed pawns. Specifically, I want to >>>know how people score pawns as they advance toward the 8th rank. How much bonus >>>do you give each square the pawn advances? Does this increase with connected >>>passers? I think Bob mentioned that if the King is defending the pawn or it is >>>blocked by an enemy piece certian bonuses/penalties are given. What do other >>>people do about this? >>> >>>Any help is appreciated. If I can get my program's passed pawn code in before >>>Thursday when I leave for the Dutch Open, I will be very happy. :) >>> >>>James >> >>James, >> >>PostModernist considers: >> >>How far away from promotion is the pawn? >> >>Is the Pawn unblocked? >> >>Is the Pawn touching another friendly passer? >> >>Is there another friendly passer on an adjacent file (but not touching)? >> >>Is it an outside Pawn with very low enemy material? (This is very >>unsophisticated at the moment in PM) >> >>Is it guaranteed to promote in a KPK endgame? (Rather crude, but reasonably >>effective). >> >>A long time ago, I got PM to analyze thousands of games (TWIC?) to give me some >>idea what these scores should be. Basically, I went through these games, looking >>for a Passed Pawn. I then "evaluated" the PP, deciding which of PM's factors >>matched the Pawn. By considering whether the game ended in a win, draw or loss >>I generated probabilities, which I converted into scores for each factor. I fed >>these scores into my program but they were no better than simply picking scores >>and tuning them. The approach didn't work well I think, because in GM games, if >>a decisive passed pawn is going to score, it rarely reaches even the seventh >>rank; the GMs both see the outcome many moves before and the loser resigns. I >>guess that apart from time-trouble cases, you generally see passers on the 7th >>only if both sides have them and both will promote. I didn't factor that into >>the assessment I was doing. Still, it was an interesting experiment. >> >>I've since changed my PP eval considerably, so the factors I now use are >>somewhat different to then. >> >>Andrew > > >beware of that "touching a friendly passer"code. IE set up a position with >the kings wherever you want, and white with passers at d2/e2, black with passers >at a7 and h7. Suddenly the connected passers lose in a big way. With pieces to >help stop those 'split passers' this is a good way to evaluate, but you _must_ >know enough to not trade your last piece (and hopefully it isn't a knight). That's a good tip. Thanks. I set up the position with White to move and it saw the impending doom after about 5 seconds. But of course it won't get that if the pos appears at the bottom of the tree. And what's worse, it thinks it is a good idea to swap off a pair of Bishops if I introduce them. Yuk. Andrew
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