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If jobz = 'V', then this array is overwritten by the unitary matrix Z which contains the eigenvectors of A. If
jobz = 'N', then z is not referenced.
So, if in your case you don't observe this feature this may be a bug. But you also should keep in mind that Divide-and-Conquer method is not the best algorithm for matrices with multiple eivenvalues.
Thanks
Victor
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