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From Gilles Sadowski <gil...@harfang.homelinux.org>
Subject Re: [math] Iterative linear solvers (MATH-581) again
Date Fri, 08 Jul 2011 10:17:45 GMT
On Fri, Jul 08, 2011 at 08:44:15AM +0200, Sebastien Brisard wrote:
> Hi everyone,
> well the message below did not raise much of an interest... My apology, I
> forgot to quote [math] in the title.
> Anyway, I have a new proposal regarding this issue. I do not know what your
> view on the subject is, but I tend to think that exceptions should return
> references and not deep copies of the objects that caused these exceptions to
> be raised. This facilitates debugging (I guess), and also helps identify the
> exact origin of the problem, without having to specialize the exception. As an
> example, Conjugate Gradient requires positive definiteness of both matrix (a)
> and preconditioner (m). If a NonPositiveDefiniteLinearOperatorException is
> caught, then I can simply test
> a == e.getOffendingLinearOperator()
> or
> m = e.getOffendingLinearOperator()
> 
> Now, coming to offending vectors, the issue is that these can either be
> instances of RealVector, or double[]. So, what type should be returned by
> getOffendingVector()?
> 
> I propose to have the exceptions return a reference to the RealVector.

It looks like the best solution.

> If the
> exception was raised with a double[], then the returned RealVector will
> actually be an instance of ArrayRealVector, with a reference to the initial
> double[]. All this is to be clearly specified in the javadoc. Does that sound
> like a viable option?
> 
> I'll attach the corresponding files to the JIRA issue, if you want to have a
> more precise idea of what I'm talking about.

Regards,
Gilles

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