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From Sébastien Brisard <sebastien.bris...@m4x.org>
Subject Re: [math] replace AbstractContinuousDistribution.getSolverAbsoluteAccuracy() with AbstractContinuousDistribution.getSolver()
Date Sat, 05 Nov 2011 17:16:00 GMT
>
> We are talking about two different things here - 0) configuring the
> solver and 1) reading its properties (in the present case, as part
> of internal implementation).
>
> Regarding configuration, the current setup where distribution
> constructors have optional inverse cum absolute accuracy arguments
> is good and should not be changed, IMO.  Users may have no idea what
> solver to use, but a good idea how accurate they want their inverse
> cum results to be, so we should keep that config option.  Allowing a
> fully configured solver to be passed in may be overkill, but if we
> want to add a protected constructor in the abstract base class and
> add implementations to all of the distributions to support it, I am
> OK with that.  Just don't drop the current simple constructors that
> either just accept defaults fully or allow the absolute accuracy to
> be passed in as a double.
>
Indeed, my idea was to keep a constructor with simple parameters for
the configuration of the default solver (Brent, in the present
implementation), alongside with a more versatile one.

I've had second thoughts about the whole thing, and came to
approximately the same conclusion as you. I've realized that
sub-classes might override inverseCumulativeProbability, and in some
cases, the new implementation of this method might do without a solver
at all (for very simple distributions). So why provide a solver at
construction time? In the present implementation, a new instance of
the default solver is created at each call.

>
> Regarding read access to the properties of the solver, another
> option is to just add a protected getSolver and be done with it.
> Alternatively, getFunctionValueAbsoluteAccuracy could be exposed
> either protected or public.  The getter for absolute accuracy in the
> distribution context really mirrors the optional constructor
> argument above.
>
> I guess my recommendation is to solve the problem we actually have
> with the simplest change, which is probably just a protected
> accessor for the solver.
>

I like the least change principle! For the reason explained above (a
solver might not always be meaningful), I would favour an accessor
like getSolverFunctionValueAccuracy(), though, instead of getSolver().
Although I don't really mind, since it would be protected anyway.

Are you OK with that?

Sébastien
> Phil
>>
>> Sébastien
>>
>>
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