[Octave-bug-tracker] [bug #59488] eigs error in dsaupd for zero matrix

[John W. Eaton]

Follow-up Comment #11, bug #59488 (project octave):

With 4.2.2:


octave:1> opts.v0 = [1;0;1];
octave:2> eigs (zeros(3), 1, 'lm', opts)
ans = 0


With 4.4.1:


octave:1> opts.v0 = [1;0;1];
octave:2> eigs (zeros(3), 1, 'lm', opts)
error: __eigs__: eigs: error -9 in dsaupd
error: called from
    eigs at line 285 column 18


With 5.2.0:


octave:1> opts.v0 = [1;0;1];
octave:2> eigs (zeros(3), 1, 'lm', opts)
error: __eigs__: eigs: error in dsaupd: Starting vector is zero
This should not happen.  Please, see
https://www.gnu.org/software/octave/bugs.html, and file a bug report
error: called from
    eigs at line 285 column 20


All on the same system with the same version of ARPACK installed from the
Debian package:


devnull:810> dpkg -l '*arpack*'
Desired=Unknown/Install/Remove/Purge/Hold
|
Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                 Version      Architecture Description
+++-====================-============-============-============================================================================
ii  libarpack2:amd64     3.7.0-3      amd64        Fortran77 subroutines to
solve large scale eigenvalue problems
ii  libarpack2-dev:amd64 3.7.0-3      amd64        Fortran77 subroutines to
solve large scale eigenvalue problems (development)


Also, for the one that succeeds, eig is called instead of __eigs__, so ARPACK
isn't even used in that case.


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