Have you taken into account the following?

ignature:      G1.spanning_trees_count(root_vertex=None)Docstring:
   Return the number of spanning trees in a graph.

   In the case of a digraph, counts the number of spanning out-trees
   rooted in "root_vertex".  Default is to set first vertex as root.


El dom, 18 jun 2023 a las 9:00, Georgi Guninski (<[email protected]>)
escribió:

> I need this for an algorithm, so even pointers to papers
> will be appreciated.
>
> The smallest bug I have is of order 36.
>
> The attached file has two multi digraphs which are isomorphic,
> but have distinct number of spanning trees.
>
>
> print("isomorphic? ",G1.is_isomorphic(G2)) #True
> print("equal trees?",G1.spanning_trees_count()==G2.spanning_trees_count())
> #False
> iso,map=G1.is_isomorphic(G2,certificate=True)
> G3=G1.copy()
> G3.relabel(lambda x:  map[x])
> print("verify iso",G3==G2) #True
>
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> .
>

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