Author: Christophe Theron
Date: 12:36:50 06/16/02
Go up one level in this thread
On June 16, 2002 at 15:24:56, Robert Henry Durrett wrote:
>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.
What do you mean?
Christophe
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