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From Luc Maisonobe <Luc.Maison...@free.fr>
Subject Re: [math] Eigen decomposition of real asymmetric matrices
Date Sun, 22 Jul 2012 16:39:02 GMT
On 22/07/2012 17:09, Thomas Neidhart wrote:
> On 07/18/2012 10:55 PM, Thomas Neidhart wrote:
>> Hi,

Hi Thomas,

>>
>> I finalized now this feature request (MATH-235) by adding more random
>> data test which success for an epsilon of 1e-12, which imho is pretty
>> good for now.
>>
>> For the problem with the internal DecompositionSolver, I now throw an
>> MathUnsupportedOperationException when trying to get a solver for a
>> decomposition with complex eigenvalues. Feedback / input to solve also
>> for the case of complex eigenvalues is very welcome.
>>
>> I will resolve the issue for now, as there was no feedback since my last
>> mail a few weeks ago. If somebody detects an issue with the current
>> implementation, please open a new issue.
> 
> it looks like this topic doesn't seem to catch lots of interest ;-).
> 
> Anyway, there is an issue MATH-651 that was about the formerly unused
> field imagEigenvalues. As we can now handle all kinds of matrices and
> the eigen decomposition can return real or complex eigen values, we have
> to provide a way for users to distinguish what kind of eigen values we
> have calculated. There are different options (with the current interface
> which we have to keep for backwards compatibility):
> 
>  - always create an imaginary value array and set it to the zero vector
>    in case of real values: requires the users to check the array for
>    zero values to see if the result is real or complex
> 
>  - in case of real values, have a null array for the imaginary part
>    getImagEigenvalue(int i) would throw an exception or return 0 in case
>    of real values
> 
>  - leave the way it is now (option 1) and provide an additional method
>    something like: boolean isResultComplex()
> 
> Any opinions?

I am not a user of this algorithm, so take my opinion only as a random
thought, not as something worth considering. I prefer to always have the
imaginary part, even if it is zero.

Luc


> 
> Thomas
> 
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