Re: variance reduction [Was Re: [Bug-gnubg] Measuring performance levels]

[Joern Thyssen]

On Mon, Oct 28, 2002 at 06:53:37PM +0100, address@hidden wrote
> 
> 
> On 24 Oct 2002 at 18:31, Joern Thyssen wrote:
> 
> > Sorry, I meant: "... since it requires 21 n-1 ply evaluations". 
> > 
> > BTW, is this actually necesary: we just want an estimate of the luck of
> > the given roll. Would it be sufficient to do a 0-ply evaluation of the
> > luck, or would that introduce bias?
> 
> A 0-ply variance reduction should be fine - it will of course be less 
> effective than a 2-ply, but also very much faster. The entire point 
> is that you can add anything which averages to 0.
> 
> I don't remember the context where Douglas asked for 2-ply VR - 
> perhaps there was a reason?

I was just browsing the variance reduction code in gnubg. I didn't
program it, I just saw that the variance reduction is performed
with n-1 ply evaluations (since you perform 21 of those it's equivalent
to a n ply evaluation). I was wondering whether this actually is
necesary. Perhaps it should be an option, e.g., one can perform a 2-ply
rollout but use 0-ply variance reduction.

Jørn

-- 
Joern Thyssen, PhD
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