Author: Christophe Theron
Date: 22:04:02 06/16/02
Go up one level in this thread
On June 16, 2002 at 18:58:08, Robert Henry Durrett wrote:
>On June 16, 2002 at 15:36:50, Christophe Theron wrote:
>
>>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?
>
>
>It was a joke. I guess I forgot to add a smiley after it. :) :) :) :) :)
>
>You asserted "I'm not the kind of guy who will stick to his beliefs until
>death." If you "really believe that" then your assertion may not be quite
>right, depending on how long you will "really believe that." Will you "really
>believe that" until death? If so, then your original assertion is contradicted.
>
>Get it? It was a joke. Ha. Ha.
>
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>
>Bob D.
Yes I understand. :)
You are right! :)
Christophe
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