[Octave-bug-tracker] [bug #41305] error: eigs: error -14 in dneupd

[Pantxo Diribarne]

Follow-up Comment #2, bug #41305 (project octave):

Just a comment : looks like the "error -14 in dneupd" (actually , "DNAUPD did
not find any eigenvalues to sufficient accuracy", see [1]) is also encountered
in matlab (see e.g. [2]). Decreasing tolerance I obtain in 3.6.4:


>> function x = func(n)
x = rand (n);
x(x < 0.9) = 0;
x(x != 0) = rand (size (x(x != 0))) - 0.5;
endfunction
>> opt.tol = 1e-5;
>> rand ("state", 137); w = func (200); eigs (w, 1)
error: eigs: error -14 in dneupd
>> rand ("state", 137); w = func (200); eigs (w, 1, "lm") %default
error: eigs: error -14 in dneupd
>> rand ("state", 137); w = func (200); eigs (w, 1, "lm", opt)
ans = -0.12943 + 1.26169i


Interestingly I don't have to decrease tolerance using the octave 3.8 (mac dmg
from octave-forge): I obtain the same complex value as in 3.6.4 with decreased
tolerance.

Having the original error message instead of the error number would help here.



[1] http://www.mathkeisan.com/UsersGuide/man/dneupd.html
[2] http://www.mathworks.com/matlabcentral/answers/100649

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