Author: Ed Trice
Date: 10:22:00 01/27/04
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Hello Dr. Hyatt , > >Crafty needs several things. > >1. Better evaluation tuning. I simply have not invested the time in this to >optimize the scoring well enough. > I was wondering if you were aware that Crafty was fine-tuned using an automated procedure that was published in: "Advances in Computer Games 10: Many Games, Many Challenges" The was the first paper appearing in this book, by Gomboc, Marsland, and Buro. It is entitled "Evaluation Function Tuning vis Ordinal Correlation." >2. No forward pruning except for null-move and futility. I haven't given this >aspect a lot of thought as I have been more interested in the parallel >programming issues. The ProbCut and MultiProbCut selected search enhancements were also used to show improvements over a vanilla version of Crafty in this book. While the gain was not outstanding, it did demonstrated that MPC could be tweaked an applied to chess (Othello was a successful testbed previously). >3. Better evaluation, period. It knows a lot about chess. And particularly >about endings. There is still much to do here and I add things as I have time >and see a problem. I see Crafty uses flat weights for the pieces and then a BADTRADE criteria to discourage certain kinds of trades. Because the number of such trades goes through the roof in Gothic Chess, I needed another technique. So, I had the piece weight change as a function of the pawn population. This does wonders for the "rook trade" problem, where B + N appears weaker than R + P, so active minors are usually disposed of for the R + P. Of course, not having the rook in the late opening or very early middlegame is not nearly as bad as being without minors that might otherwise have very good prospects. Since you can tweak the weight of any chess piece very granularly, you can have the Queen gradually gain strength as pawns come off of the board, and have Knights weaken. Bishops can usually stay the same since they are given mobilty bonuses. --Ed
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