[igraph] about rewire fuction

[Qunawei Zhang]

Hello:

In the manual it said "Simple rewiring algorithm which chooses two arbitrary edges in each step (namely (a,b) and (c,d)) and substitutes them with (a,d) and (c,b) if they don’t yet exist."

How do you determine which node is "a" given an edge? "a" is always the node with smaller ID than "b"?

For a undirected graph, after we randomly selected two edges (namely (a,b) and (c,d)), I think we can substitutes them with (a,d) and (c,b) or (a,c) and (b,d). We should give both substitution the same chance.

Given two edges, if the "a" node and "c" node are not randomly determined (for example, "a" and "c" are always the one with the smaller ID of the two nodes connected to an edge), then when we do rewiring we do not consider all possibilities for a undirected graph.

Do you agree? And would you please tell me where can I find the source code of rewire function? I want to look at the details. 

Thanks

Best

Quanwei