Author: Dann Corbit
Date: 12:35:16 11/08/01
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On November 08, 2001 at 12:43:23, Uri Blass wrote: >On November 08, 2001 at 11:04:59, Mark Young wrote: > >>On November 08, 2001 at 10:20:37, Uri Blass wrote: >> >>>I define a real sacrifice of chess program as a move that is losing material >>>based on only material evaluation but is played by the program because the >>>positional score is bigger than a pawn. >> >>Most of the Real sacs I have seen are based on mating attacks. Do you define >>this as a real sacrifice? > >If the program can see the mate or can see material that it get I define it as a >combination and not as a real sacrifice > >The test if it is a real sacrifice can be done by a materialistic program with >good search rules(positional scores always lower than 0.5 pawn so we can know >the material score based on the score of the program). > >If the materialistic program can only see that the sacrifice is losing material >even after a long search then it is clearly a real sacrifice. I think by your definition, a chess sacrifice by a computer would be where the positional score is more than a pawn (piece?) even though the material goes negative. I have seen lots of things like this in Crafty, but it is usually only a pawn or so rather than a full piece. So I guess those are really gambits, rather than sacrifices. Colin's program Beowulf can have some very large positional scores. If you look at the code where board control is computed, you will see that a single simple aspect like that can be worth much more than a pawn. Probably all good programs would "sacrifice" under this definition, given the right circumstances. I say that because if you have a material only eval, the moves chosen will be wildly different from a good eval plan. In fact, any program that uses material only eval is sure to lose to any decent chess program. A clear, numerical definition of what you mean by sacrifice would help, I think. Another interesting test would be to take a dozen "classical" sacrifices by Morphy, Fischer, Tal, whatever, and run them through computer programs. See which programs make the same moves (if any). I suspect that sometimes what we perceive as a sacrifice by a great player was a very deep tactic, which the superGM saw all along. The Evergreen game is one that computers see through. And one of the compelling sacrifices in the sequence in that game is refused by the computer (which wrecks the whole thing). Good thing it wasn't two computers that were playing it.
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