Author: Bruce Moreland
Date: 17:09:45 12/14/00
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On December 14, 2000 at 19:02:53, Dieter Buerssner wrote: >On December 13, 2000 at 22:33:27, Bruce Moreland wrote: > >>My program was down a couple of pawns against Crafty in an opposite bishop >>ending with rooks on the board, when suddenly it traded off a couple of pawns, >>traded off the rooks, ran with its king into a corner, and declared the position >>equal: >> >> 8/8/3b4/8/7k/6pp/8/5B1K w - - 0 1 >> >>I couldn't figure out why it was smart enough to have a draw score for this >>position, then it occurred to me that Crafty has B + wrong RP :-) > >Nice story - really. But would you like to elaborate, by which means your >program detected the draw. Without the black g pawn, it seems rather easy, >but with this pawn ... >Or did I totally misunderstand you post, and this was the subject of the bug? > >Regards, >Dieter Actually I am a little confused. There was no bug, the program was correct. What my code says is: If we are in an opposite bishop ending, and it's two pawns to zero, if one of the pawns is a wrong rook pawn, and the king is in position to block it, score it as a draw. This works great if the white king is on h1, there's a pawn on h4 or so, and there's a b-pawn. The white bishop can sacrifice itself for the b-pawn and the game is a draw. The program knows this in eval. I figure that by just doing the opposite B case, it is very safe to score this as a draw, since it is very easy for the bishop to sacrifice itself for the pawn in all but very freakish cases. It didn't occur to me that it also works perfectly if the pawns are connected. It was really very beautiful to watch, I love it when my program understands cases where the opponent says +3. bruce
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