Author: Andrew Williams
Date: 03:25:31 10/27/99
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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
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