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From Thomas Neidhart <>
Subject Re: [math] Eigen decomposition of real asymmetric matrices
Date Sun, 22 Jul 2012 15:09:27 GMT
On 07/18/2012 10:55 PM, Thomas Neidhart wrote:
> Hi,
> 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?


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