Author: Robert Hyatt
Date: 07:59:26 12/16/05
Go up one level in this thread
On December 16, 2005 at 01:47:14, Stuart Cracraft wrote: >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. As I said, it has been known for years. Berliner was the first to put it in writing that I know about, but most everyone has stumbled over this at some point, and it causes great problems... > >> >>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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