Hi, I'm using the BGL to explore an implicit graph. At the beginning, I only have one node, and no arc. And I instanciate new nodes and their corresponding arc on-the-fly in the A* visitor ( in examine_vertex ). However, the A* algorithm internally uses this queue : MutableQueue Q(num_vertices(g), icmp, index_map); which means that I'm supposed to : - know how many vertices I'm gonna need during the search, which I don't - Instanciate them all... Any hints here ? Notes : I use astar_search_no_init, and property maps based on std::map so that put() can index it in a not-known-yet location. Btw, my color map type is std::map<NodeID,boost::default_color_type > (plus the wrapper around it). I feel that using "boost::default_color_type" is kind of a hack. Is it ? Thanks Arnaud Arnaud