Author: Robert Hyatt
Date: 09:01:24 11/27/02
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On November 27, 2002 at 09:49:55, Bob Durrett wrote: > >Disclaimer: I do not know the specifics of how position evaluation is >accomplished in the top chess engines. > > >From what I have read here, position evaluation is typically accomplished with a >"function." This function appears to be fairly simple. Otherwise it would be >called a position evaluation "subprogram." Since a large number of positions >are evaluated, the evaluation must be very quick and hence simple. > >Less processor time is available for searching if the amount of processor time >used for position evaluation is increased. In an extreme example, one might >devote 90% of the processor time to position evaluation. I do not know what >this percentage is in practice. If a huge number of positions are evaluated, >then the total amount of processor time devoted to evaluation might be large. > >It seems that there is a tradeoff between complexity of position evaluation and >the number of positions evaluated. My impression is that current engines devote >only a very small percentage of the processor time to evaluation of any given >position. > >Devoting a large amount of processor time to position evaluation of each >individual position would make sense, or so it seems, only if the evaluation >were very very good. Essentially, this would mean evaluating only a relatively >few positions but evaluating them extremely well, using a complex position >evaluation subprogram. > >In theory, a perfect evaluation subprogram would have to evaluate only one >position for each move made. Maybe someone would say that chess engines do just >that. They "evaluate" the position after the move was made. They just do it >using search algorithms. > > >So, this leads to the following question: > >Has anybody yet explored the option of using complex evaluation subprograms >[which do not rely primarily on the use of search algorithms] for position >evaluation? > >Bob D. You definition of "simple" is very vague. For example, is Crafty "simple" or "complex"?? Whichever you choose, Crafty spends over 50% of the total time used for selecting a move in executing the evaluation code. I have a hard time calling 50% of the total time "simple" myself, since this is about 4,000 lines of code, roughly...
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