Author: Ed Schröder
Date: 09:33:06 04/08/04
Go up one level in this thread
On April 08, 2004 at 12:07:13, Tord Romstad wrote: >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 There is an easy way out, just classify them suitable for an "indirect call" using "switch-case", see: http://members.home.nl/matador/chess840.htm#INTRO Ed
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