[Octave-bug-tracker] [bug #31479] Crash & bugs in eigs

[John W. Eaton]

Follow-up Comment #12, bug #31479 (project octave):

I've checked in the changes.  Unfortunately, just after checking them in, I
noticed that I'm sometimes getting this:


A = [1,0,0,-1;0,1,0,0;0,0,1,0;0,0,2,1]; [vecs,vals,f] = eigs(A,1)
vecs =

  -1.0000e+00
  -5.8044e-12
  -3.9807e-12
   1.9951e-06

vals =  1.0000e+00 + 3.4557e-06i
f = 0
error: eigs: error -8 in dneupd


This is quite odd, as I thought I was using the same sources for ARPACK as
the debian package, which is what I was using before.  I'll try to debug
later.

The comments in dneupd say that error -8 is


Error return from calculation of a real Schur form.
Informational error from LAPACK routine dlahqr


Hmm...


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