Here is the problem: I would have imagined that, in my case,
boost::num_vertices(graph) would have returned 6, but it actually returns
the higher vertex number + 1, that is... 4243 ! So each of my vector has a
size of 4243 * sizeof(tVertex) bytes... Is there a way to handle that? I
probably misuse the API, but it would be better if the container would be
dimensioned to the actual number of vertices, since I am in a CPU and memory
constraint environment...
You're confusing the notions of "index" and "descriptor". With the vertex set using vecS, the descriptor of a vertex is the same as its index -- hence the confusion. Therefore, when you call add_edge(4242, 1, ...), the graph thinks you mean the vertex whose descriptor is 4242 and resizes itself accordingly.
You have to remember - whatever the examples may indicate - that you should never actually use a literal value and descriptors interchangeably. This isn't documented very well, either.
You could use a std::map to associate your own identifiers with vertex descriptors.