I am not sure I understand how Networkit handles the names of the nodes.
Let's say that I read a large graph from an edgelist, using another Python module like Networkx; then I convert it to a Network graph and I perform some operations, like computing the pairwise distances. A simple piece of code to do this could be:
import networkx as nx
import networkit as nk
nxG=nx.read_edgelist('test.edgelist',data=True)
G = nk.nxadapter.nx2nk(nxG, weightAttr='weight')
apsp = nk.distance.APSP(G)
apsp.run()
dist=apsp.getDistances()
easy-peasy.
Now, what if I want to do something with those distances? For examples, what if I want to plot them against, I don’t know, the weights on the paths, or any other measure that requires the retrieval of the original node ids?
The getDistances() function returns a list of lists, one for each node with the distance to every other node, but I have no clue on how Networkit maps the nodes’ names to the sequence of ints that it uses as nodes identifiers, thus the order it followed to compute the distances and store them in the output.
When creating a new graph from networkx, NetworKit creates a dictionary that maps each node id in nxG to an unique integer from 0 to n - 1 in G (where n is the number of nodes) with this instruction.
Unfortunately, this mapping is not returned by nx2nk, so you should create it yourself.
Let's assume that you want to get a distance from node 1 to node 2, where 1 and 2 are node ids in nxG:
import networkx as nx
import networkit as nk
nxG=nx.read_edgelist('test.edgelist',data=True)
G = nk.nxadapter.nx2nk(nxG, weightAttr='weight')
# Get mapping from node ids in nxG to node ids in G
idmap = dict((id, u) for (id, u) in zip(nxG.nodes(), range(nxG.number_of_nodes())))
apsp = nk.distance.APSP(G)
apsp.run()
dist=apsp.getDistances()
# Get distance from node `1` to node `2`
dist_from_1_to_2 = dist[idmap['1']][idmap['2']]