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## [igraph] an ad-hoc edge property similar to weight

 From: heroxbd Subject: [igraph] an ad-hoc edge property similar to weight Date: Mon, 30 May 2011 19:22:47 +0900 User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux)

```Dear Guys and Girls,

I am using igraph (via python) for several months for graph
clustering. It really rocks!

I have a tree with weighted-edges, and want to calculate weight times
the smaller number of vertices of the two components if the edge is
deleted:

,----
| def sep(graph, e):
|     h = copy(graph)
|     w = h.es[e]['weight']
|     h.delete_edges(e)
|     return w * min(h.components().sizes())
|
| # 'graph' is the tree I am dealing with
| ss = [sep(graph,x) for x in range(len(graph.es))]
`----

My questiones are:

1. Is this a known (and named) property in graph theory? If so, what is
it?

2. My piece of code is very inefficient if I calculate this for all the
edges, as shown above. If the graph becomes 50000 edges and vertices,
memory consumption becomes huge. Do you have some suggestions for
optimizing?

Cheers,
--
XU Benda
Research Center for Neutrino Science
Tohoku University
JAPAN

http://www.awa.tohoku.ac.jp/~benda

```