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Re: [igraph] page.rank speed
From: |
Tamás Nepusz |
Subject: |
Re: [igraph] page.rank speed |
Date: |
Wed, 31 Jul 2013 22:23:33 +0200 |
> page.rank has been running forever:
[...]
> on
>
> IGRAPH DN-- 12062801 15279166 --
> attr: name (v/c)
>
> is this normal?
Not sure but I wouldn't rule it out -- your graph is pretty large and ARPACK
can be a tad bit slow. I have just tried it on an Erdos-Renyi graph of similar
size and it also did not terminate for a while. On the other hand, you might be
experiencing a convergence issue with ARPACK. Sometimes it happens that ARPACK
fails to detect convergence (at least within the machine epsilon) and performs
the maximum number of allowed iterations with essentially no improvement after
the first few iterations -- then it bails out with a warning saying that the
maximum number of iterations has been reached. Try increasing the epsilon value
a bit when invoking page.rank() to see if it terminates faster or not. Or
decrease the maximum number of iterations allowed. I'm not familiar with the R
interface but I think there is an options=... argument to page.rank where you
can specify some options that ARPACK will use.
An alternative solution if you are feeling adventurous and you don't mind
compiling igraph from source: try the 0.7-prpack branch of igraph (downloadable
from Github):
https://github.com/igraph/igraph/tree/0.7-prpack
This branch uses the excellent PRPACK package instead of ARPACK to calculate
PageRank scores. PRPACK does all sorts of neat tricks to ensure faster
convergence for PageRank calculations. The branch will be merged with the 0.7
development tree sooner or later but it still needs more testing.
All the best,
Tamas