Author: Tord Romstad
Date: 14:36:15 04/08/04
Go up one level in this thread
On April 08, 2004 at 12:33:06, Ed Schröder wrote: >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 Hi Ed, Did you intend to link to some other section of your pages? Perhaps I'm just too tired, but I can't see that the link you provide has any relation whatsoever to the topic under discussion. Tord
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