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Date: Sat, 01 Oct 2011 13:44:32 -0700
From: Phil Steitz <phil.steitz@gmail.com>
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To: Commons Developers List <dev@commons.apache.org>
Subject: Re: [math] rename o.a.c.m.linear.SingularMatrixException to
 SingularLinearOperatorException
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On 10/1/11 1:21 AM, S�bastien Brisard wrote:
> Hello,
> I need to be able to throw an exception when an iterative linear
> solver detects that a RealLinearOperator is singular. I would propose
> to implement a SingularLinearOperatorException. Then, since RealMatrix
> is derived from RealLinearOperator, it would be logical to have
> SingularMatrixException inherit from SingularLinearOperatorException.
> However, looking at the present impl of SingularMatrixException, this
> exception does nothing fancy. So having two different exceptions might
> be too much, I don't know.
> So here are two proposals
> 1. Rename SingularMatrixException to SingularLinearOperatorException
> 2. Create SingularLinearOperatorException, and have
> SingularMatrixException extend SingularLinearOperatorException.
>
> Which option (or any other) do you favor?

I would keep it simple and just have the two exceptions
independent.  The reason for this is that the activation contexts
are likely to not often have much in common - i.e., as we have
discussed before, a singular matrix exception will be triggered when
a matrix that is not supposed to be singular is numerically singular
(usually with some kind of threshold) while a singular operator
exception is going to be triggered when an operator acts
singularly.  Of course, if the operator is represented by a matrix,
then the specialization makes sense; but this will not always be the
case, so there is not going to be meaningful state or implementation
inheritance.  Therefore I don't see much value in the inheritance
(think about the value of catching the superclass or inheritance of
state or implementation in the exceptions themselves).  I would also
shorten the name to SingularOperatorException.

Phil
> S�bastien
>
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