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From Gilles Sadowski <gil...@harfang.homelinux.org>
Subject Re: [Math] "NonPositiveDefiniteMatrixException" message and meaning
Date Fri, 09 Sep 2011 11:39:02 GMT
On Thu, Sep 08, 2011 at 04:55:46PM -0700, Ted Dunning wrote:
> OK.
> 
> Replace that with the correct value.  I meant it to be an index.
> 
> That doesn't change my other points.  There is an inherent problem with
> "less than" comments when you have subtracted several other elements
> previously and only now notices that the remainder is less than some other
> adjusted value.  The user cannot relate either value back to anything that
> they have and they may well look at their own matrix and see the opposite
> condition.  It is better to give a slightly more abstract message such as
> "Non-positive definiteness in input detected at diagonal element number xxx"

What do you think of the following message?

<element value> is smaller than, or equal to, the minimum (<threshold value>):
not positive definite matrix: value <element value> at index <element index>

where, in actual messages, the <...> will be the numeric values of course.

"NonPositiveDefiniteMatrixException" would inherit from
"NumberIsTooSmallException". The rationale being that it exactly matches the
test and that it is meaningless to report an element of the original matrix,
as you've explained.

> [...]

Gilles

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