Re: [igraph] A few questions

[Tamas Nepusz]

> I'm trying to decide between using igraph and boost graph. I
> saw a comparison [1] of igraph (sna) against several other
> graphing solutions, and was wondering if the benchmarks could
> be updated to include boost. Would be good information to
> have on the main web page.
I'll keep it on my TODO list. The reason why I didn't include BOOST in
the comparison in the paper you mentioned is that I had to finish that
paper in about two days and I had no previous experience in BOOST - it
would have taken a whole lot of time :) Personally I expect igraph to
be faster than BOOST in most of the cases, since the former is written
in C and the latter in C++ with lots of templating stuff, but of
course this has to be benchmarked thoroughly. If there is anyone out
there among the members of this mailing list who is more experienced
in BOOST than me, it would be great if he/she could sketch up some
quick benchmarks for BOOST regarding (for instance) diameter
calculation, PageRank, closeness centrality, edge betweenness or
whatever BOOST supports.

> Also, I see in layout.c that igraph_layout_springs is not
> yet implemented. Would it be possible to use some of the
> ideas from graphopt [2] (it's c++)?
I think yes, sooner or later :) One of the reasons why the springs
layout is not implemented yet is that we did not really need it so
far, the Fruchterman-Reingold and Kamada-Kawai layouts (based on the
same principles) were pretty satisfactory, and for very large graphs
(where these two layouts are way too slow) there is the grid-based
Fruchterman-Reingold layout and the Large Graph Layout (see
http://lgl.sourceforge.net/), both implemented in igraph.

> Finally, are there plans to add support for ogdl [3]?
I don't think support for this format will be included directly in the
trunk in the near future (unless someone sends us a patch which does
not add dependence on libogdl - we are trying to keep library
dependencies to a minimum). However, using the code from libogdl, I
think it would be easy to sketch up a converter from OGDL to a more
specific graph format - the OGDL parsing is done by libogdl, and by
conducting a BFS or DFS traversal of the resulting Graph structure
(see http://ogdl.sourceforge.net/api/c/graph_8c.html), one can easily
transform it to an edge list or something similar. Labeled edge lists
can then be imported by igraph using igraph_read_graph_edgelist().

-- 
Tamas