Author: Robert Henry Durrett
Date: 12:24:56 06/16/02
Go up one level in this thread
On June 16, 2002 at 13:08:18, Christophe Theron wrote: >On June 16, 2002 at 02:46:50, Peter McKenzie wrote: > >>On June 15, 2002 at 14:28:36, Christophe Theron wrote: >> >>>On June 15, 2002 at 13:44:06, Russell Reagan wrote: >>> >>>>On June 15, 2002 at 11:36:29, Christophe Theron wrote: >>>> >>>>>About the "fork" example: I would not treat it by evaluation. I have tried and >>>>>it does not work. The solution of this problem must be found in search or >>>>>QSearch improvements. >>>> >>>>Why doesn't it work? It seems to me that as long as you are able to hammer out >>>>the details of detecting forks and special cases you should be able to implement >>>>this (or any other tactical recognition) statically in the evaluation function. >>>> >>>>Of course, I have never tried it myself, so you surely know better than I do, >>>>but I'm curious if you could provide us with some information as to WHY it won't >>>>work. Is it because there are too many special cases to handle to make it >>>>accurate? >>>> >>>>Thanks, >>>>Russell >>> >>> >>> >>>It is because there are a lot of special cases to handle. If you want to >>>substract the value of a whole piece from your evaluation, you'd better be sure >>>about what you do, or else you will screw up many times. >>> >>>So it's hard to write and consumes a lot of processing time. >>> >>>You end up with something really expensive in term of processor time, that you >>>have to do at every leaf node or almost, and that is useful (if it works) only >>>in a tiny fraction of the positions you examine. >>> >>>It's a clear loser. >>> >>>There are more generic search algorithms, which take care not only of forks but >>>also of many other tactics, which are less expensive computationally, and which >>>are a much better solution for this problem. >>> >>>In general, trying to take tactics into account in the evaluation function is a >>>bad idea. >> >>In general, statements such as the above are a bad idea :-) >> >>You have a fantastic program, so you clearly have an approach that works. >>Great, but does that mean it is the only approach that works? I doubt it. >> >>You have tested many things, and obviously some work for you and some don't. >>Does that mean that the things which didn't work for you could never work, or >>wouldn't work for someone else? Of course not. A chess program is such a >>complex system of interworking components, that every program is different and >>what works in one might not work in another. >> >>The relationship between nullmove and q-search is a case in point. Maybe Bob's >>simple QSearch is why nullmove pruning wasn't great for him on slow hardware. >> >>One of the cool things about computer chess is the diversity of different >>approaches to the problem. Look at some of the top programs for example: Tiger, >>Fritz, Hiarcs, Junior, Shredder. I bet there is alot of variety in those >>programs! We have Fritz's big speed, Junior's weird search, Tiger's big >>pruning, Hiarc's slow NPS (who knows what he is doing), and Shredder which I >>don't know much about. >> >>And then there are even more 'way out' programs like CSTal, Diep, etc. >> >>Just my 2 cents worth. >> >>See you in Maastricht. > > > >I just wanted to share my experience. > >Sorry if I sound patronizing, I understand it can be unpleasant. > >You can add an implicit "In my opinion" at the start of every sentence I write. > >If you knew me better you would know that I question everything I do or believe. >All the time. > >I still believe Tiger is far from optimal and I am sure there are things I'm >doing really badly. > >Sometimes I tend to believe that my search is rather good, and sometimes I >believe it really sucks. Actually most of the time. > >After all it's just a work in progress. > >When I match Tiger against Genius on a slow computer for example, I can SEE that >my search sucks. I'm trying to improve it but all the time I have the feeling >that I'm missing something obvious. So far I have not found what. > >It is true that there are some ideas that I defend strongly, but I'm just >waiting for somebody to help me change my opinion. Even if I do not give >technical details about what I do, I keep on discussing ideas here and I expect >to get good feedback and reasons to change my mind. > >I'm not the kind of guy who will stick to his beliefs until death. Do you really believe that? Bob D. > >Being stubborn in achieving a goal is a strength. Being stubborn in beliefs is a >weakness. > >I'm the kind of guy whose strong point is that I can change my mind, admit I was >wrong, and move forward. > >That's what makes me dangerous. :) > > > > Christophe
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