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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] inconsistency in fast eigen decomposition
- From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
- Date: Thu, 3 Feb 2011 08:24:58 -0500
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Could a unit test be added? Maybe just take his matrix, decompose,
reconstruct original matrix, compare. My understanding is that before
your fix, eigen would have given a completely wrong reconstructed
matrix, so just a fuzzy compare at default test precision would be
good enough.
Benoit
2011/2/3 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>:
> yes but was is strange in Radu's example is that the direct method
> find a negative eigenvalue while they should all be positive (or equal
> to zero). I guess that's because of the multiple trigonometric
> functions. Anyway, now I start to compute the eigenvectors from the
> biggest eigenvalue and compute the last eigenvectors from the first
> two while taking care of some degenerated cases.
>
> gael
>
> On Thu, Feb 3, 2011 at 1:52 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
>> Yeah, it's hard to be accurate when there are degenerate eigenvalues.
>> Radu's example had well separated eigenvalues.
>
>
>