Hello,
I am trying to build the non-backtracking matrix of a network. It is the matrix whose entries are indexed by the edges of the graph. Entries are 0 if the said edges do not form a path of length two, and 1 if they do. More details can be found in arXiv:1306.5550, p3.
All the algorithms I could produce are very slow. Computing the entries is not a problem, however storing them properly in the matrix is, and takes a lot of time.
I would welcome any suggestion on the topic.
Best,
Pierre-André Maugis