Hi there, Has anyone worked on very dense graph ? Basically the relation is implicitly given by the position in the grid: Eg, consider the following structured grid A B C D E F G H I it would lead to the following (undirected) graph: Graph g(9); add_edge(A, B, g); add_edge(A, D, g); add_edge(B, C, g); add_edge(B, E, g); add_edge(C, F, g); add_edge(D, E, g); add_edge(D, G, g); add_edge(E, F, g); add_edge(E, H, g); add_edge(F, I, g); add_edge(G, H, g); add_edge(H, I, g); When the structured grid is full (no broken link) I would think there are better data structure (ie. no data at all) suited to represent the graph. And as we break link (say, edge(A,B)), we would use an opposite definition of adjacency_list, to list what edge is actually *missing*. As far as I know adjacency_matrix is not implemented in PBGL, so I'll need to work around that issue /real time soon/. Thanks for your help, -- Mathieu