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Subject: Re: Branche factor

Author: James Robertson

Date: 18:12:09 11/21/99

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On November 21, 1999 at 18:57:56, Bert van den Akker wrote:

>On November 21, 1999 at 16:37:52, Daniel Clausen wrote:
>
>>Hi
>>
>>On November 21, 1999 at 16:04:39, Peter Kappler wrote:
>>
>>>On November 21, 1999 at 14:59:53, Bert van den Akker wrote:
>>>
>>>>From the start position I get a branche  factor of about 14%
>>>>
>>>>This is in a 10 ply search from the start position.
>>>>
>>>>The branche factor is defined as:
>>>>
>>>>(total_number_of_moves_looked_at_in_a_node_before_cutoff /
>>>>total_number_of_generates_moves) * 100
>>>>
>>>
>>>This is how I used to compute branching factor, too.  I still think it's the
>>>best way to measure the quality of your move sorting.
>>
>>I've no "experience" in computing a branching factor, but this formula looks a
>>bit
>>strange to me. I would have expected an absolute number, not a percentage.
>>
>>And consider the following: Let's say you try the move in the hashtable first
>>and you
>>get a cuttoff. (That's what you want in most cases.) According to your formula
>>you
>>get a branching factor of 100% - I think you'd like to get a small percentage
>>though!
>>
>>>But, I think most programmers measure branching factor by dividing the total
>>>number of nodes search at depth n by the number searched at depth n-1.
>>
>>This formula seems to be very intuitive to me.
>>
>>Kind regards,
>> -sargon
>
>
>Before I try the hash move I first generate all moves.
>So the percentage will be ok.
>
>In my example on ply 10
>27632 moves from the hashtable were causing a cutoff.
>
>Not generating all moves would save me around 0.15 second.
>
>My move generator can generate 200000 times all moves in the start
>position.
>
>BvdA

It is a much better plan to try the hash move before generating all moves. :)

James



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