Hi, I have the following code using Boost Graph Library to use the breadth-first-search: -------- code start -------- template<typename T> class MyVisitor : public boost::default_bfs_visitor{ public: MyVisitor(T& d): boost::default_bfs_visitor(),d_(d) {}; template<typename E, typename G> void tree_edge(E e,const G& g) const { typedef typename boost::graph_traits<G>::vertex_descriptor VD; VD u = boost::source(e,g); VD v = boost::target(e,g); d_[u].parent_ = v; }; private: T& d_; }; ... typedef boost::adjacency_list<boost::listS // out-edges , boost::vecS // vertex set , boost::undirectedS , boost::property<boost::vertex_name_t,IndexT> , boost::property<boost::edge_name_t,IndexT> > GraphT; ... typedef boost::graph_traits<GraphT>::vertex_descriptor VD; ... struct DataMap { DataMap(VD p):parent_(p),distance_(0){}; DataMap():parent_(0),distance_(0){}; VD parent_; int distance_; }; ... typedef std::vector<DataMap> VisitedT; typedef VisitedT::iterator VisitedIterT; // Graph g properly initialized here VisitedT visited(boost::num_vertices(g)); for(VI i=vertices(g).first,iend=vertices(g).second;i!=iend;++i){ visited[*i].parent_=*i; }; MyVisitor<VisitedT> vis(visited); boost::breadth_first_search(g,boost::vertex(0,g),boost::visitor(vis)); -------- code end -------- The compiles OK, but when I run it I got: Assertion failed: (std::size_t)i < pm.n, file C:/boost_1_46_0/boost/graph/two_bit_color_map.hpp, line 86 which is strange as I do not tweak with the color map. From the trials it seems that the "VisitedT" works if it holds "simple" types like vertex decriptor etc and not aggregates. My intention with the DataMap to register the vertex parents and the vertex distance at the same time, when the edge is visited. Is there any limit on the library side or did I something wrong? Thank you and regards, K