Author: Stuart Cracraft
Date: 22:47:14 12/15/05
Go up one level in this thread
On December 15, 2005 at 21:52:49, Robert Hyatt wrote: >On December 15, 2005 at 21:01:00, Brian Richardson wrote: > >>On December 15, 2005 at 20:03:47, Sergei S. Markoff wrote: >> >>>>Really? Just the line from fruit:eval.c: >>>> >>>> eval = ((opening * (256 - phase)) + (endgame * phase)) / 256; >>> >>>No. Not just this line, but the concept and well tuning. >>> >>>>I find that VERY hard to believe. That concept has been around a >>>>very long-time. >>> >>>Really? Where it was introduced by the first time? >> >>Don't know about the first time, but GNUChess (v4) uses the same approach, >>albeit only for some king eval terms, and many programs scale things by >>material, although not necessarily as nicely as Fruit does. > >Most all programs use something similar. You can't afford to have >discontinuities in the evaluation or when you are in positions that are right >around the discontinuity, you will get some really bizarre results as the search >will find ways to creatively cross over the discontinuity when it seems >favorable, to produce a big score change over nothing. Bob - this is a *great* explanation. Good reason to implement it asap. > >Crafty has lots of terms that "scale" by material. Kingsafety drops off as >material goes away. Endgame features (pawn majorities, outside passed pawns, >etc) scale up as material goes away. This is not new... I think Berliner first >mentioned this "problem" 25 years ago in some paper or another...
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