distance_map is extremely slow

[clbarnes]

Using networkx's shortest_path_length is extremely slow for this data; the "classic" algorithm should be much faster (but the current implementation is incorrect).

I believe that the problem with the python implementation of the classic distance_map algorithm is the sorting of the partitions. The JS docs say that they should be sorted in order of length, but I think they should actually be ordered topologically. partitions_sorted should return the root-containing partition last.

[clbarnes]

the "classic" algorithm should be much faster

It's not.

[unidesigner]

I have not looked into the algo itself, so I can't tell. Maybe this is useful regarding faster implementations
https://stackoverflow.com/questions/938338/what-is-the-fastest-dijkstra-implementation-you-know-in-c
Maybe @ceesem can also comment.

[clbarnes]

Just a thought - this might be at least in part because the reference implementation constrains the maximum length of a path, where I'm not currently doing that in the ArborNX implementation.