Author: Robert Hyatt
Date: 11:38:11 09/24/98
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On September 24, 1998 at 12:00:03, Amir Ban wrote: >On September 24, 1998 at 11:43:38, Robert Hyatt wrote: > > >>This last influences the evaluation of the above position quite markedly, >>because this is an endgame, and black is going to get the bishop-over- >>knight in endgame bonus two times since black has two bishops, white has >>none. Black also gets the traditional bishop-pair bonus as well, which >>might or might not be overkill here. In any case, I first gave this to a >>GM to look at and the response "black wins easily." Not surprising, the >>bishop pair vs the pair of knights should favor the bishops. I then told >>him that Crafty "statically" evaluates this position as "-.93" which is >>the raw score Evaluate() returns here. He said "hmmm... ". And we had >>an interesting conversation without concluding whether this is too large, >>too small, or "just right." >> > >The expression "black wins easily" should translate to -2.50 at least. > >I see a gross contradiction between "black wins easily" and "-0.93 is just >right". > >Amir He didn't say -.93 is just right at all. He said "hmmm..." when I gave him that number. Here is how the conversation went, sort of edited and paraphrased to make this shorter: H: what do you think about this position? Don't look at deep stuff, just a quick glimpse, followed by a "gut-feel." Got that? GM: yes, show me the position. <showed> GM: black wins easily. Two bishops vs two knights, no obvious pawn weaknesses. Hmmm... I hope you aren't going to tell me that there is some 20 move combination that lets white win here? H: No... ok... next question. Crafty says -.93 here (both of these GM's knew what this meant, having played Crafty thousands of games and having watched it play about that many as observers). GM: Hmmm... <pause> I think black is better than "just a pawn up." H: hmmm... my concern here is that this evaluation is not based on shuffling the pieces around to see if there are tricks... Therefore, I am skeptical about making this too large a positional score, because that could lead to problems like reaching this position a pawn down, for example. What would you do if the black a-pawn is missing? Or the black f-pawn? GM: that changes things. OK... maybe we agree that black is winning. Whether your score should be -.5 or -1 or -999 is maybe more complicated than I thought, because I don't quite understand how computers search these positions and how they use this "number" to figure out what to play. I have an idea, but barely an idea. <eot> So he didn't agree nor disagree... He basically agreed with the "sign" of the score (black is winning) but the magnitude was another issue. The conversation with the other GM went similarly. Which is why I posted this. Note that the original ICCA article was written by a GM, which is what caught my attention when I was flipping thru old issues yesterday...
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