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

Author: Stuart Cracraft

Date: 18:21:48 12/28/05

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On December 28, 2005 at 16:25:02, Uri Blass wrote:

>On December 28, 2005 at 16:04:28, Tord Romstad wrote:
>
>>On December 28, 2005 at 15:31:55, Roman Hartmann wrote:
>>
>>>On December 28, 2005 at 15:27:34, Dann Corbit wrote:
>>>
>>>>How are you calculating mobility?
>>>>A 10:1 loss in speed is very traumatic.
>>>>Unless you are only counting wood in your evaluation, you should not see that
>>>>traumatic of a degradation.
>>>
>>>Several problems:
>>>-outdated board design 10x12
>>
>>16x12 may be slightly more convenient, but 10x12 isn't outdated
>>at all.  There is no reason why mobility evaluation should be expensive
>>on a 10x12 board.
>>
>>>-legal move generator instead of pseudo legal
>>
>>You shouldn't generate moves at all when evaluating mobility.  This
>>is almost certainly the main reason why you see such a big slowdown.
>>When you generate moves, you do a lot of work which is not necessary
>>when you just want to evaluate mobility.  You don't need the moves
>>at all, just the number of moves.  Perhaps you can even omit some
>>piece types.  I don't evaluate pawn or king mobility at all (in my
>>experience, there are better ways to evaluate king activity), and I
>>have never seen any measurable difference in strength when I
>>switch queen mobility on or off.
>>
>>Tord
>
>I also do not see a reason for slow down that is so big.
>
>being 1.3 times slower make sense but not being 10 times slower.
>
>Note that the idea of not calculating mobility for pawns or for the king is idea
>that I learned from fruit that I also think to try.
>
>originally it was hard to do it because of the bad design of movei but I believe
>that after the changes that I did it may be easier to do it later in Movei.
>
>Uri

Trying to understand nps differences is a recipe for no happiness.

I have changed my tune and advocate looking at play quality too.

Don't slip back where I used to be too.

Stuart



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