Re: [Help-gsl] wrong eigenvalues?

[Brian Gough]

Michael Gross writes:
 > Hello (gsl 1.4, suse 8.2, make check is ok)
 > 
 > When I replace the Matrix in the example on
 > http://sources.redhat.com/gsl/ref/gsl-ref_14.html#SEC235 with:
 >    double data[] = { 1, 2, 3,
 >                      4, 5, 6,
 >                      7, 8, 9};
 > 
 > (and replace the 4 in the gsl-calls with 3) then I get the
 > eigenvalues: 18.8302, -3.15747 and -0.672768.  The polynom of the
 > matrix is 18*l+15*l^2-l^3 so one eigenvalue has to be 0.  Matlab
 > (and Maple) calculates (eig([[1 2 3];[4 5 6];[7 8 9]])) the
 > eigenvalues 16.1168, -1.1168 and -0.0000.
 > 
 > What is wrong?

Hi,

gsl_eigen_symmv computes the eigenvalues of a symmetric matrix.

If the matrix is not symmetric (as in this case) then the results are
undefined.

regards

-- 
Brian Gough