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[Octave-bug-tracker] [bug #55710] svd may sometimes return -0 for exactl
[Octave-bug-tracker] [bug #55710] svd may sometimes return -0 for exactly zero singular values
Thu, 14 Feb 2019 13:44:10 -0500 (EST)
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Follow-up Comment #4, bug #55710 (project octave):
1) I agree that this -0 is likely to be an upstream issue with LAPACK.
Fortunately, it's easy to fix so I imagine it won't be too long from them to
handle it on their end.
2) In the meantime, having Octave implement a temporary workaround would be
ideal. It's debatable which is better but I think S(S==0)=0 is better than
abs(S). I doubt there's a difference speedwise. But if there's ever a bug
where the SVD routines return a negative singular value, with S(S==0)=0, that
negative value would still get passed to the user so someone might actually
notice something is really wrong. With abs(S), we'd never know.
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