Author: Daniel Kang
Date: 11:22:23 11/19/00
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On November 19, 2000 at 13:37:32, Ricardo Gibert wrote: >On November 18, 2000 at 17:57:51, Daniel Kang wrote: >>Wouldn't it be even better if it gave the expected value of a match? Since, in >>practice, chess is a game of incomplete information (at this point, chess is >>solvable only in theory), isn't it better to judge a position by the possible >>outcomes and how likely each outcome is, rather than its absolute theoretical >>value, which neither the program or its opponent can be expected to compute? > >Consider K+R vs K. Most legal moves by the superior side are winning moves and >the expectation of winning for each of those moves are about 100%. How do you >tell the difference between the moves that bring you closer to mate and the >moves that are winning, but prolong the game? > >The term "evaluation" is something of a misnomer and as it used in computer >chess, which is significantly different from how human players use it. A better >name is perhaps "preference-score". Naturally, a program will/should have higher >scores for those positions that bring the game closer to mate. This is what is >"preferable". You're right. You need to be able to tell how close a position is to the outcome, if you already know what it's going to be. I didn't mean to exclude that information (it just hadn't been mentioned at the time and almost all evaluation heuristics need an explicit way to deal with it). It's just my opinion that the widely-used piece-value heuristics might not be the best way to base one's evaluation on. It was mostly designed to tell if having a rook is about as good as having a knight and two pawns, but not whether being up by a rook is as good as being up by a knight and two pawns, etc. I'm writing this after Crafty just dropped a game (1 min per 40 moves, but my point about the eval function stands) against GNU Chess where it was consistently up by about 9 (Crafty would probably have resigned if it were on the other side). In my opinion, a score of +3 or so should be a near certain win and beyond that, the exact amount of material one's ahead by ceases to be the primary factor. Dan.
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