Hi,
just forwarding the suspicion of igraph upstream that the problem is
caused by arpack. I'm tempted to reassign bug #902760 but I'd like
to hear your opinion first.
Kind regards
Andreas.
----- Forwarded message from Tamás Nepusz <notificati...@github.com> -----
Date: Thu, 26 Jul 2018 11:19:03 -0700
From: Tamás Nepusz <notificati...@github.com>
To: igraph/igraph <igr...@noreply.github.com>
Cc: Andreas Tille <ti...@debian.org>, Author <aut...@noreply.github.com>
Subject: Re: [igraph/igraph] Testsuite fails with ARPACK 3.6 (#1107)
Okay, I am pretty certain that this is an inherent issue with ARPACK 3.6; the
same problem can also be triggered in GNU Octave (4.4.0) when linked with
ARPACK 3.6 (I tried it on a Mac with Homebrew). The code below produces the
PageRank matrix of the graph from the igraph test case:
```
octave:1> m = ones(11, 11) * 0.15 / 11;
octave:2> m(1, 2:11) += 0.85;
octave:3> m(2:11, 1) = (1 - m(1, 1)) / 10;
```
and it blows up exactly the same way:
```
octave:4> [v, lambda] = eigs(m, 1)
error: __eigs__: eigs: error -9999 in dnaupd
error: called from
eigs at line 285 column 18
```
I'll file a bug report to `arpack-ng`.
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