[igraph] why is igraph_rewire_edges so fast?

[sizheng0320]

Hi everyone,

has anyone read the code of the function igraph_rewire_edges?

i'm doing this because i wonder why this function rewires a large network so fast. 

it seems some indexing technique is used, because i have seen in the function igraph_i_rewire_edges_no_multiple in games.c, some vectors such as first, next, prev are used. 

though i tracked the code with a small network of 5 nodes and 6 edges, i still don't understand the meaning of the three vectors. How do they work, please?

Thanks a lot!

Gang Lu