[igraph] Problem with Graph.Adjacency

[Jonathan Donges]

Dear Tamas,

I once again encountered a problem with the Graph.Adjacency function  
of the igraph Python interface v0.6, using Mac OSX. I usually create  
and store the adjacency matrix in Numpy int8 format to save memory for  
large networks.

Then

>>> a = numpy.array([[1,0,1],[0,1,0],[1,0,1]], dtype="int8")
>>> g = igraph.Graph.Adjacency(list(a))

produces

__main__:1: Warning: non-numeric value in matrix ignored

and

>>> print g
Directed graph (|V| = 3, |E| = 0)

On my local MacBook, it works when a.dtype = "int32". However, on our  
64bit Linux cluster, only a.dtype = "float64" works, wasting a lot of  
memory.

Do you have any idea, what could be the cause of this issue?

Thank you very much!
Jonathan