Author: Robert Hyatt
Date: 20:16:13 12/07/02
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On December 07, 2002 at 22:11:01, Mike S. wrote: >In a WinBoard match game Delfi 3.2 - Crafty 18.15, the following position >occured before the 92nd move, after Crafty allowed it's last pawn to be >exchanged (maybe that was forced, though don't think it was, didn't analyse >it): >[D]R7/3b1k2/8/6R1/4r2K/7P/3r2P1/8 w - - 0 92 >Crafty, but also other engines, evaluate that position with a *big* advantage >for black, sometimes up to -2.x. No combination involved (the material balance >didn't change the next 80 moves). If Crafty says black is winning, something is broken as there is specific code to handle that particular case (one side is a minor piece up but with no pawns it has no chance of winning even if the opponent didn't have any pawns left... I'll look to see if I broke something... although 18.15 might be old enough that the fix was not in... > >4-piece tbs. + RB-R, RN-R were installed. > >I'd like to ask strong chessplayers especially, but also anybody else, if the >following is correct: > >1. Since RB-R is a theoretical draw (with few exceptions), the value of the >black bishop is *less* than usual here. >2. White's pawns are connected passers and therefore *more* valuable than +2. >3. Crafty knows the basic RB-R draw within it's algos (IIRC; I didn't check it >now) and will evaluate it correctly even in the quiescence search. >4. For these reasons, the position should be evaluated less (for Black) than the >material balance, IOW between 0.00 and -1.00 (max.) if not with a white >advantage even (White's pawns seem to be more dangerous than Black's bishop). > >Does the presence of the additional 2 rooks change the evaluation that much? We >have RRPP vs. RRB. I wonder if something "anti human" in Crafty might be >responsible for the too optimistic evaluation... Black has the potential to >create mate threats still, easier than in RB-R. > >The game lasted until move no. 227 (!!) until it was finally drawn... > >Regards, >M.Scheidl
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