Re: [eigen] 3x3 symmetric eigenvalues Problem
• To: eigen@xxxxxxxxxxxxxxxxxxx
• Subject: Re: [eigen] 3x3 symmetric eigenvalues Problem
• From: Manuel Yguel <manuel.yguel@xxxxxxxxx>
• Date: Wed, 2 Nov 2011 13:17:32 +0100
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```I got it: it is the default value for significantSquaredNorm2 that is
too high for that case.
The matrix is normalized therefore, the matrix that is actually investigated is:
diag( 1, 5e-4, 0 )
Now the squared norm of the cross product between col(0) and col(1) is
lower than Eigen::NumTraits<typename
Matrix::Scalar>::dummy_precision() hence the matrix is considered as
equivalent to diag(1,0,0) and the result is correct from that point of
view.
If you change the default value for significantNorm2 to
Eigen::NumTraits<typename
Matrix::Scalar>::dummy_precision()*Eigen::NumTraits<typename
Matrix::Scalar>::dummy_precision()
it is ok.
There is another problem now for almost isotropic matrices:
the precision_for_isotropic_case set to dummy_precision is too large
for those matrices (I did not realize that before, hmppffff)
If I change the line
if( Q < Scalar(0) ) to if( Q <= Scalar(0) )
in the code computing the roots of the polynomial
everything is ok for those matrices
however I think a better criterion is needed here but I have to make
some calculations and tests which will wait until this week-end.

- best regards,

Manuel

```

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