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Date: Sat, 02 Jun 2012 09:19:41 +0200
From: Luc Maisonobe <Luc.Maisonobe@free.fr>
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To: Commons Developers List <dev@commons.apache.org>
Subject: Re: [Math] About MATH-798
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Le 02/06/2012 01:55, Gilles Sadowski a �crit :
> Hello.

Hi Gilles,

> 
> Do you know the rationale behind the (very) small values for
>  DEFAULT_RELATIVE_THRESHOLD (set to 100 * Precision.EPSILON)
>  DEFAULT_ABSOLUTE_THRESHOLD (set to 100 * Precision.SAFE_MIN)
> in "AbstractConvergenceChecker"?
> [I created this class as part of a refactoring, but the values were carried
> over from whatever class contained that functionality before.]
> 
> With those values, the "GaussNewtonOptimizer" fails to find the solution but
> if one changes the threshold to either
>  1e3 * Precision.EPSILON (for the relative threshold)
> or
>  1e281 * Precision.SAFE_MIN (for the absolute threshold)
> the solution is found in 4 evaluations!
> 
> As I wrote on the user ML, the thresholds were too stringent.
> Are the current values really suitable as defaults (in other part of the
> library, similar defaults are much larger)?
> [I even think that there shouldn't be any defaults, so that users are
> actually aware that the thresholds are problem-dependent and sometimes even
> optimizer-dependent. My preference would thus be to deprecate the default
> constructor in all the checker classes.]

I think I wrote the initial classes, and I picked the values from a
domain-specific case. So from a general point of view, these values are
probably worthless.

OK for deprecating in 3.1 and suppressing the values in 4.0.

Luc

> 
> 
> Best regards,
> Gilles
> 
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