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Subject: Re: Branching factor, etc

Author: Ralf Elvsén

Date: 08:11:50 08/31/02

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On August 31, 2002 at 05:34:11, Uri Blass wrote:

>On August 31, 2002 at 04:51:49, Ralf Elvsén wrote:
>
>>On August 30, 2002 at 23:00:30, Andreas Herrmann wrote:
>>
>>>On August 30, 2002 at 21:03:25, Uri Blass wrote:
>>>
>>>>>>
>>>>>>I know this :-)
>>>>>>
>>>>>>But there is the odd/even issue, so the b-factor can change drastically while
>>>>>>moving from an odd ply to an even ply, and vice versa.
>>>>>
>>>>>I think the best is to calculate an average branching factor from all plys.
>>>>>
>>>>>bf[avg] = ( bf[2] + bf[3] + bf[4] ... + bf[n] ) / (n - 1)
>>>>>
>>>>>Andreas
>>>>
>>>>It is better to use
>>>>( bf[2] * bf[3] * bf[4] ... * bf[n] )^(1/(n-1))
>>
>>Not if the numbers bf[i] are ratios of the type bf[i] = T[i]/T[i-1] (e.g.)
>>Then everything will cancel out except for the first and last T[i]
>
>I think that this is exactly the idea about branching factor.
>The question is if I need 1 second to get depth 1 how many seconds I need to get
>depth n.
>
>It is also possible to use the formula (T(n)/T(1))^(1/n-1)
>
>Uri


Well, it all depends on what you want. I personally wouldn't like this
measure to depend heavily on T(1) which I would expect to vary much.
And if you have a series for T which is

T1 = 1 T2 = 2 T3 = 4 T4 = 16 T5 = 64

and another

T1 = 1 T2 = 4 T3 = 16 T4 = 32 T5 = 64

then you have very different branching factors for low/high plies
(relatively speaking) but the proposed formula gives the same
overall value. So you are throwing away information and (in my
opinion) relies heavily on a suspect value: T(1).

Just my opinion...

Ralf



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