Author: Robert Hyatt
Date: 08:07:43 10/27/99
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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).
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