Re: [Boost-users] [Boost.Graph] Accessing edge properties via an edge_iterator

I wonder what is the fastest method to access edge properties of an adjacency_list when iterating over edges. Actually, the only way I know of for accessing properties is via operator[]:

typedef boost::adjacency_list Graph;

Graph g;

for( tie( ei, ei_end ) = edges( graph ); ei != ei_end; ++ei ) { g[*ei]=something; }

From this I conclude, that the right EdgeProperty is stored in some associative container, with edge_descriptor being the key-type. Or does edge_iterator store any information besides a pair? What is the time complexity of this look_up?

To me it feels that there should be a faster way to access properties via an edge_iterator, and by browsing the source I found that edge_iterator has a member function get_property(), however, since it returns void*, and I did not find anything in the documentation, I'm not sure if it is there for this purpose.

That's probably the best way to think of it. For an adjacency_list, the edge descriptor is actually a triple of (u, v, p), where p is a pointer to the stored edge property. Operator[] just deref's that pointer, giving you the edge property in constant time. Andrew Sutton andrew.n.sutton@gmail.com