Author: Tord Romstad
Date: 09:07:13 04/08/04
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On April 08, 2004 at 07:58:31, martin fierz wrote: >On April 08, 2004 at 04:51:01, Albert Bertilsson wrote: > >>Hi! >> >>I'm about to start coding on my engine again and have thought about improving >>the endgame play. I don't like using egtb so I'm thinking about using special >>evaluation cases when there are few pieces left on the board. Is this a good >>idea or is special evaluation cases a dead end? > >i do the same. my problem is that i have only covered a couple of special cases >up to now, and not in much detail. another problem is that many things are still >the same for all endgames; e.g. it is nearly always good to have a centralized >king, and it is always good to have passers and candidates and so on. however, >for example the value of a passer depends on the endgame type. so you need some >kind of strategy for computing common things for all endgames, and only doing >some special stuff for the special cases. because if you want to write an entire >eval for every type of ending, your code will get HUGE :-) > >i still haven't figured out a really good way to do this myself, my code is a >bit of a mess in this respect :-( > >but in principle, i believe that you need special knowledge for different >endings. there *are* huge differences between different types of endgames, and >this leads to eval discontinuities - but i'm pretty certain that you shouldn't >worry about this. there is the "eval discontinuity = evil" fraction here with >bob as spokesperson. but as a chess player i can assure you that these >discontinuities are absolutely real, and IMO a good evaluation should know about >them... The discontinuities are definitely real, but the problem is that when you have several sub-evaluation functions for different classes of endgames, it becomes painful to make the jumps in the eval have the right magnitude, or even the right sign. In principle it is always possible to make it work well, but in practise the job of tuning it all is a nightmare. The worst thing of all is that it is not possible to solve the problem once and for all. When you tune some weights in your eval for one particular class of endgames, you will often be forced to tune the weights in many related endgames as well. Tord
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