Re: [eigen] Help Eigen - eigenvalues and eigenvectors

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On 21.01.2014 11:59, Nicolas BOUSSONNIERE wrote:
Results (values D and vectors V for matrice A) between the two executions
(with -O2 first and with -g second) are differents (and with a big
difference for eigenvectors) !

Do you have eigenvalues which occur multiple times are very close? Then any linear combination of the corresponding eigenvectors is also a valid eigenvector, and Eigen might choose a different due to small numerical differences. Another possibility is that an eigenvector is only different by sign. Furthermore, the order of the eigenvalues is not guaranteed by EigenSolver, so you might want to sort them anyways.

I don't know which is the best result because all seems good :
A = V D V-1
and || V || = 1

Do you expect anything more from the result?


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