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[Octave-bug-tracker] [bug #49523] eigs (R2013b and later) uses NaNs, not
[Octave-bug-tracker] [bug #49523] eigs (R2013b and later) uses NaNs, not zeros, for unconverged Ritz values
Fri, 1 Dec 2017 00:36:15 -0500 (EST)
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Follow-up Comment #52, bug #49523 (project octave):
Maybe Carlo has an idea on how to relax this. I found that by increasing the
maximum number of iterations, opts.maxit, ARPACK would converge and find all
the eigenvalues. That is not what is needed here.
I restored maxit to 1, and then started changing the initialization vector v0.
For some vectors there was rapid convergence and I got the three eigenvalues
listed in comment #50 (although they were all real, no imaginary parts).
Maybe there is a specific initial vector which is always far enough from a
solution that the answer from comment #46 is obtained.
Otherwise, we could work around it by coding the BIST test like this
if (isreal (d))
assert (d(4), NaN);
assert (d(4), NaN+1i*NaN);
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