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

Author: Dann Corbit

Date: 17:51:22 12/28/05

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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.

>>So...
>>
>>Big_again:
>>Tell the program that a knight is worth 'start' (e.g. 200) centipawns.
>>Have it try to solve 12000 positions at depth k.
>>Count the solutions.
>>
>>Little_again:
>>Tell the program that a knight is worth Current Knight value + Increment
>>centipawns.
>>Have it try to solve 12000 positions at depth k.
>>Count the solutions.
>>
>>If current knight value is bigger than 'limit' (e.g 500) goto Little_again
>>
>>Fit the curve and write the solution. (We are interested in the apex of a
>>parabola that has only a maximum and not a minimum.)
>>
>>If depth is not at maximum desired depth, increment depth 'k' and goto Big_again



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