Author: Robert Hyatt
Date: 06:09:02 09/17/99
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On September 17, 1999 at 03:15:53, Bruce Moreland wrote: >On September 16, 1999 at 23:59:25, Robert Hyatt wrote: > >>First, a little background. I have been doing 'outside passed pawn' scoring >>for years now, because I got tired of seeing Crafty lose endings where it was >>a pawn up, and it traded down to the point where it was a king and pawns vs >>king and pawns ending, where the opponent had an outside passed pawn that made >>it an easy win... >> >>OK... that was fairly easy to code using bitmaps... and it has worked well. >>But once you get past that hurdle, you begin to see endings where you trade >>down to a pawn-up ending, but your opponent has a queen-side majority that >>turns into an outside passer outside the search horizon, and the same issue >>comes up again. >> >>I am working on addressing this now, and am looking for a discussion on what >>might be the best way to do this. >> >>I have completed a fairly accurate 'candidate passed pawn' analyzer. It is >>in the EvaluatePawns() code so that it is all hashable and won't cost a fortune. >> >>All it does is simply look at each pawn that has no enemy pawn in front of it, >>and decides whether pushing that pawn can make a passer or not. Again, not >>hard using bitmaps, and in studying the results, it looks reasonable. My intent >>is to use this in the absense of any outside passed pawns for one side, to see >>if it has any potential outside passed pawns on that side of the board. And >>for the usual 3 vs 2 queen-side majorities, it works cleanly and accurately. >> >>But what about 4 vs 3? Where the passer ends up on the d-file, which might >>not be far enough away to cause problems. Or what about 3 vs 3, where one >>side has pawns on a-b-c, the other side has pawns on b-c-d, and both end up >>with a passer although the abc passer will be more distant. >> >>I guess my question is, has anyone given any thought to this? Or is anybody >>even dealing with pawn majorities at present? I tend to not actually call this >>majority code any longer, because it is _really_ candidate passed pawn >>evaluation instead... >> >>My intention is to recognize that if the kings are on g1/g8, and white has >>the a-b-c pawns and black just has b-c pawns, that this is a nearly winning >>position. I am going to do just like I do with outside passers, that is, have >>their value go up as material goes down, as they don't mean much with queens and >>pieces on the board... >> >>Any comments, suggestions, ideas, etc? >> >>Obviously necessary, yet I don't see any evidence that any program does much >>with this excepting for deep blue... > >I had a nice routine that detected viable candidates, but it was very slow so I >threw it out. > >So as of now my program doesn't do a good job with majorities. > >Once pawns become passed it tries to be intelligent about king location relative >to the pawns. > >But yes, this could be a source of improvement. > >Don't write your code in such tricky fashion that you start trading your e-pawn >for the opponent's a-pawn, etc. > >bruce That's the reason I initially planned to not factor this in to the evaluation until material starts getting low. IE my outside passed pawn values are very small (.1 at best) until much of the material is gone... because I saw some very silly things happen before I did that..
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