Author: Christophe Theron
Date: 10:08:18 06/16/02
Go up one level in this thread
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.
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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