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Subject: Re: How is Hydra faster and better than Deep Blue?

Author: Gian-Carlo Pascutto

Date: 15:40:21 05/30/05

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On May 30, 2005 at 17:44:03, Ricardo Gibert wrote:

>>No.  In fact it increases it significantly.  In Cray Blitz, it reduced our
>>average search depth about 2 plies.  Which is a significant _increase_ in
>>effective branching factor.
>
>Most extentions result in a reporting of lower depth and an increase in nodes,
>but this usually still means a reduction in ebf, because the depth reported does
>not take into account the additional depth from the extentions. In short, the
>depth reported underrepresents effective depth. As for SE I don't much about it,
>but it must be a pretty crappy extention if it really increases EBF.

By this redefinition of EBF, I don't immediately see how any technique *can*
have any effect on the EBF.

An extension would decrease the nominal depth, but this "doesn't count", because
the amount of nodes searched stay the same and the effective depth is deeper.

A pruning would increase the nominal depth, but that doesn't count either,
because the effective search depth is deeper.

Even nullmove probably doesn't improve the EBF here - the reduced depth searches
mean that the effective depth is also significantly lower.

What you're saying is that the NPS is constant, I think. Yes...but...so what?

I don't think that your line of reasoning makes any sense. And I also really
fail to see how the usefulness of an extension can be defined by it's effect on
the branching factor.

--
GCP



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