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| From: | David Bateman |
| Subject: | [Octave-bug-tracker] [bug #57196] eigs should detect symmetric/hermitian inputs and return real values only |
| Date: | Tue, 12 Nov 2019 05:51:48 -0500 (EST) |
| User-agent: | Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Firefox/60.0 |
Follow-up Comment #2, bug #57196 (project octave):
Page 51 of the ARPACK user guide discuss why this is the case
https://pdfs.semanticscholar.org/1ac9/6899e1c355d78b55ad6b1cc038493de4a906.pdf
Basically the hermitian and non hermitian complex versions of ARPACK are the
same cost in terms of computation and so they only implemented one of them.
The manual just suggests ignoring the non zero imaginary part for hermitian
problems. So using "real" on the eigenvalues is in fact the "right" solution,
but should probably be implemented in __eigs__ rather than eigs.
David
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