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Subject: Re: Branching factor of alpha-beta

Author: Sune Fischer

Date: 09:44:42 08/23/01

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>>I just upgraded my little engine from using a negamx to an alpha-beta algorithm.
>
>Negamax _is_ alpha/beta.  It is just re-formulated so that + scores are
>always good for the side on move in the tree.  Normal alpha/beta has +=good
>for odd plies, -=good for even plies, which makes the code messier.

I thought that negamax was minimax, only "re-formulated".


>Normal alpha/beta should give you an effective branching factor of about
>sqrt(x) where x is the effective branching factor of pure minimax.  That
>ought to be somewhere around 6-10 max.

I thought that was a theoretical best and only if I have a perfect moveordering
(which of cause I never do).

>Most everyone uses negamax as the framework.  Whether you use simple
>alpha/beta on top of that, or something more sophisticated (I use PVS for
>example) doesn't change the look of the basic search that much.

Okay thanks.



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