'predecessors' argument to igraph_get_shortest_paths[_dijkstra]

[Tamás Nepusz]

When running the single-source shortest path (SSSP) algorithm from Python on a large graph, most of the time is actually spent not by finding the paths but by converting the path vectors to Python lists. A lot of time could be saved by allowing the user to query the "predecessor vector" instead of the actual paths. The i-th element of the predecessor vector would simply be the index of the vertex that is the predecessor of vertex i in the SSSP tree or -1 if the vertex was not reached. (The predecessor of i is of course i itself).

We could simply add this feature by adding a third argument called "predecessors" besides the existing "vertices" and "edges" arguments in the C layer.

[Gábor Csárdi (gabor.csardi)]

Fine with me.

[Gábor Csárdi (gabor.csardi)]

Do you want to do this for 0.6-main?

[Gábor Csárdi (gabor.csardi)]

The development of igraph has moved to github, so please do not comment on this bug here. You are of course welcome to comment on github, here:
https://github.com/igraph/igraph/issues/222