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Subject: Re: move ordering and node count

Author: Dan Andersson

Date: 11:01:20 03/29/04

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>
>in any case, you can now assume that you find the best move 1st in the fraction
>F (~0.9), and in the remaining case at random, this leads to
>
>nodes(depth) ~ (N*(1*F+(N/2*(1-F)))^D/2.

 This is a flat distribution for the rest of the moves. A reasonable argument
can be made for some other kind of distribution.
 F.ex.: The next move has the success rate of F. Thus the mean number of moves
tried will be close to one for any reasonably large F.

MvH Dan Andersson

>
>plugging in some numbers like N=20 (reduce from 40, trying to account for
>nullmove?!), D=10, F=0.90 and 0.91 i get
>
>nodes(10, F=0.90) = 79 million
>nodes(10, F=0.91) = 62 million
>
>so for 1% better move ordering i get 22% less nodes?! seems rather excessive.
>let me try again using sqrt(N) instead of N/2 - that still gets a 12% reduction.
>



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