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Re: [igraph] page.rank speed


From: Giulio Valentino Dalla Riva
Subject: Re: [igraph] page.rank speed
Date: Sun, 5 Jan 2014 19:05:22 -0800 (PST)

P.S. same problem with eigenvector centrality, slightly different error
Error in evcent(Graph, directed = TRUE) : At arpack.c:1178 : ARPACK error, Unknown ARPACK error


On Monday, 6 January 2014 16:02:03 UTC+13, Giulio Valentino Dalla Riva wrote:
Probably is a bit late but... was the ARPACK error solved?

I'm working with R 2.15.3 and the last CRAN version of igraph (0.6.6) and, on a small 161 directed graph with 592 links still gives me a
Error in page.rank(Graph) : At arpack.c:1178 : ARPACK error, The Schur form computed by LAPACK routine dlahqr could not be reordered by LAPACK routine dtrsen.

The graph is connected. If you want I can send you the graph...

Best wishes,

Giulio

On Saturday, 3 August 2013 07:18:01 UTC+12, Tamás Nepusz wrote:
>  At arpack.c:1178 : ARPACK error, The Schur form computed by LAPACK routine dlahqr could not be reordered by LAPACK routine dtrsen.
Seems to be a long-standing issue with ARPACK and we haven't figured out yet how to solve this; see, e.g.:

https://bugs.launchpad.net/igraph/+bug/365817
https://github.com/igraph/igraph/issues/385

It seems to occur on relatively sparse graphs and it also seems that removing isolated vertices usually resolves the problem. Also, the issue will probably not come up again if we switch to PRPACK. Can you try removing any isolated vertices in your graph (if any) and try again? If it still fails, send me your graph somehow and I'll investigate.

--
T.


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