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Subject: Re: Mobility in Chess Evaluation Function at terminal-nodes

Author: Stuart Cracraft

Date: 18:26:23 12/28/05

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On December 28, 2005 at 20:51:22, Dann Corbit wrote:

>On December 28, 2005 at 19:56:16, David Dahlem wrote:
>
>><snip>
>>
>>>The idea works like this:
>>>Suppose that I evaluate a pawn as 100.0 centipawns.  How much should a knight be
>>>worth?  Probably somewhere between 200 and 500 centipawns.  Now, if I choose a
>>>bad value (like 200 centipawns) then I should solve less problems.  If I choose
>>>a good value (probably fairly close to 300), then I will solve more problems.
>>>So I iterate over 12,000 quiet chess positions with known solutions and see what
>>>value of the parameter gives me the most solutions.
>>>
>>>Now, the value found will NOT be optimal for play.  But it will be a good
>>>starting point for experimentation.  And I will also have a pretty good idea
>>>about what sort of range will produce reasonable results.
>>>
>>
>>Thanks Dann. I'm not really a fan of tuning with test suites. I just build
>>several test versions with different bonus values, and run a lot of test games.
>>It's time consuming, but i have more confidence in the results. :-)
>
>I agree that test suites are not good for game play.  But they are useful to get
>an idea of the general ballpark for the right value of a parameter.
>

True - it is cheaper and easier to graft onto a program test-suite capability.

But, for real study, I advocate using things like Genetic Algorithms,
Temporal Differences, and other methods for tuning evaluation function
parameters and coming to best results.

I do not like to hand-tune as you can tell.

The methods above may take as much time to initially program but can give
unattended results that are as good as hand-tune (with less guilt/ongoing
maintenance.)

Stuart



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