Am 21.04.20 um 06:17 schrieb Deklan Webster:
Once I corrected that error by only sampling edges which don't have a reciprocal the performance between undirected/directed mostly disappeared. So, performance still bad. To ensure it wasn't just my network or something to do with directedness I tried several simple undirected graphs from graph-tool's collection (where I don't need to worry about multiedges). All performed poorly.
Regardless of your claimed performance, I still think it's pointless to comment on unseen code.
The directed SBM does not generate reciprocal edges very well, hence it is not a good predictor in this case.
Where can I read more about this? I assumed the SBM handles the directed case just fine, even if there are many reciprocal edges. Does this have implications for community detection as well?
The SBM does not distinguish between nodes that belong to the same group (and have the same in/out-degrees in the degree-corrected version), and places edges in a conditionally independent manner. Therefore even if the probabilities are symmetric between two groups in both directions, the probability that exactly the same edges are placed in both directions is very small. The consequences for community detection are the same for other small-scale structure not captured by the SBM (e.g. triangles): edge reciprocity is not used to find comnunities. Best, Tiago -- Tiago de Paula Peixoto <tiago@skewed.de>