[igraph] Reproducibly computing Kamada-Kawai layout?

[Jan Kim]

Dear All,

exploring the layout_kamada_kawai method of the igraph.Graph class in
Python, I can't seem to find a way to reproduce a layout. The graph is
always the same (to the extent I can visually tell), but the placement
of vertices is different each time.

I tried specifying the seed parameter as follows:

    s = []
    s.append(range(len(g.vs)))
    s.append(range(len(g.vs)))
    l = g.layout_kamada_kawai(seed = s)

but the layout is still different each time.

The best educated guess I have at this point is that the iterative
vertex placement by simulated annealing involves stochastic elements
in addition to the initial placement, but I can't seem to find any
way to locate the pseudorandom number generator used for such purposes,
so I could take control of it / its seed.

As the documentation on the seed parameter "If a matrix (list of lists),
uses the given matrix as the starting position" is not entirely unambiguous
to me, I also tried the transposed version of that generated above:

    s = []
    for i in xrange(len(g.vs)) :
      s.append([i, i])

but the layouts still differ each time.

Any suggestions / RTFMs welcome.

Best regards & thanks in advance, Jan
-- 
 +- Jan T. Kim -------------------------------------------------------+
 |             email: address@hidden                                |
 |             WWW:   http://www.jtkim.dreamhosters.com/              |
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