page.rank caused unknown ARPACK error

[Casper Petersen]

Given a large (1.4 million edges), connected, directed, unweighted graph in the edgelist format "imported" using read.graph with the latest igraph (igraph 0.5.4) causes the following error:

g <- read.graph("cts.txt", format="edgelist", directed=TRUE);
k <- page.rank(g, v=V(g), directed=TRUE);
Error in page.rank(g, v=V(g), directed = TRUE):
At arpack.c:586 : ARPACK error, Unknown ARPACK error

I found a previous bug-report concerning this, where the user was advice to use igraph 0.6 - maybe I have missed something but that does not seem to exist.

[Tamás Nepusz (ntamas)]

There is a bug in igraph 0.5.4 due to which an incorrect error message is shown in this case; the real error message would be as follows:

"The Schur form computed by LAPACK routine dlahqr could not be reordered by LAPACK routine dtrsen."

Anyway, the solution to this issue would be to raise the "ncv" parameter of the underlying ARPACK routine, but this is unfortunately not yet possible in igraph 0.5.4. We are currently fixing issues with eigenvector calculations for the upcoming igraph 0.6 release. igraph 0.6 is not released yet, but you can give it a try by installing it from source; the nightly snapshots are to be found here:

http://code.google.com/p/igraph/downloads/list

Alternatively, please send me the graph you are working with, I'll calculate the PageRank values for it and send them back to you. This would also help us confirm that igraph 0.6 will not have problems with graphs like yours.

[Tamás Nepusz (ntamas)]

I will be deploying some changes to the eigenvector calculations today, so if you want to try out igraph 0.6, maybe it's best to wait for tomorrow's nightlies because those will include these changes.

[Casper Petersen (e-blade)]

Thanks a lot for the feedback. I'll give the snapshot a go later on, but otherwise I may take you up on your offer.

[Melissa Lim (mlim)]

I'm also having problems using page.rank on a directed, unweighted graph. My edgelist also read in from a file. I'm using igraph 0.6-2 with R 2.15.1. My test graph isn't that large: 1392 vertices and 2896 edges.

The error I get is:

Error in page.rank(mygraph) :
  At arpack.c:1126 : ARPACK error, Unknown ARPACK error

Ideas? Thanks.

[Tamás Nepusz (ntamas)]

Please upload your graph here or send it to my private email address (see my profile) so I can take a closer look at it. Also, it would be helpful to know what OS you are running R on.

[Gábor Csárdi (gabor.csardi)]

The development of igraph has moved to github, so please do not comment on this bug here. You are of course welcome to comment on github, here:
https://github.com/igraph/igraph/issues/451