Hi Alex and all,

Examine Vertex

vis.examine_vertex(u, g)

void

This is invoked on a vertex as it is popped from the queue. This happens immediately before examine_edge() is invoked on each of the out-edges of vertex u.

"Examine" seems to work once on first encounter (is that correct??) so might worth a try.
I did try the code below but I got errors on the part the works with the color map. Any ideas?

class dijkstra_2step : public boost::default_dijkstra_visitor
{
public:
    dijkstra_2step(std::vector<Weight> dists, double threshold): distances(dists), threshold(threshold) {}

    void examine_vertex(boost::graph_traits <unGraph>::vertex_descriptor u, const unGraph& g){
        boost::property_map< unGraph, boost::vertex_color_t >::type colorMap = boost::get(boost::vertex_color, g);
        if( distances[u] > threshold ) colorMap[u] = boost::color_traits::black();
    }
    std::vector<Weight> distances;
    double threshold;
};


Thanks