How is it possible to get an estimate for the memory requirement of a graph in graph-tool?

I know that graph-tool is built upon C++ and Boost, and the adjacency list is stored via a hash-map.

Apart from the cost of storing the values of vertices indices and edges indices as `unsigned long`, what is the memory overhead of the structures used in storing the graph?

For example, for a network of 1M vertices and 100M links without attributes, how much real memory should I plan to use, excluding temporaries?

Sorry if the question is repeated, but I could not find it in the previous mailing list posts.

Regards,

Carlo