Re: [igraph] ARPACK error in igraph 0.6

[Tamas Nepusz]

Hello,

ARPACK seems to throw up on some degenerate graphs; this is known but we
haven't figured out yet what can be done about it. One of our users has even
had a graph where the full graph threw an ARPACK error, but removing any
arbitrary edge from the graph resolved the problem:

https://bugs.launchpad.net/igraph/+bug/365817

I don't know what could be causing this, but if you are willing to share the
graph with me (just upload it somewhere where I can download it and send the
URL to my private email address), I'll take a look.

Also, may I ask you which igraph function are you trying to run on the graph
when you get this error?

Cheers,
Tamas


On 11/16/2011 01:22 AM, Leo Alekseyev wrote:
> I am trying to compute the page rank of a graph with ~50,000 vertices
> and 300,000 edges.  I'm using the R interface to the latest nightly of
> igraph (igraph_nightly_0.6-2591-20111110).  I keep running into the
> following error:
> 
> At arpack.c:961 : ARPACK error, The Schur form computed by LAPACK
> routine dlahqr could not be reordered by LAPACK routine dtrsen.
> 
> After some googling, I tried increasing the ARPACK iteration limit by
> settting igraph.arpack.default$maxiter <- 50000, but it didn't help.
> 
> Any suggestions about dealing with the error are appreciated :)
> 
> --Leo
> 
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