使用两个访客提升图形库

Question

After some tests I observer that the stamp_times visitor is the problem:

typedef adjacency_list <vecS, vecS, undirectedS> Graph;
typedef graph_traits <Graph>::edge_descriptor Edge;
typedef graph_traits <Graph>::vertex_descriptor Vertex;


Graph g(edges.begin(), edges.end(), n);

typedef graph_traits <Graph>::vertices_size_type Size;

std::vector<Size> dtime(num_vertices(g));
Size time = 0;

breadth_first_search(g, s, visitor(make_bfs_visitor(
                       stamp_times(dtime.begin(), time, on_discover_vertex()))));

(I got more less the same error with that code).

I need to use two visitors one to record predecessors and a second one two obtain visiting time.

boost::breadth_first_search
    (g, s,
     boost::visitor(boost::make_bfs_visitor
            (std::make_pair(
            boost::record_predecessors(&p[0], boost::on_tree_edge()),
            stamp_times(dtime.begin(), time, on_discover_vertex())))));

But this code event do not compile. I get following error.

/usr/include/boost/graph/visitors.hpp: In member function ‘void boost::time_stamper<TimeMap, TimeT, Tag>::operator()(Vertex, const Graph&) [with Vertex = long unsigned int, Graph = boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS>, TimeMap = __gnu_cxx::__normal_iterator<long unsigned int*, std::vector<long unsigned int> >, TimeT = long unsigned int, Tag = boost::on_discover_vertex]’:
/usr/include/boost/graph/visitors.hpp:109:8:   instantiated from ‘void boost::detail::invoke_dispatch(Visitor&, T, Graph&, mpl_::true_) [with Visitor = boost::time_stamper<__gnu_cxx::__normal_iterator<long unsigned int*, std::vector<long unsigned int> >, long unsigned int, boost::on_discover_vertex>, T = long unsigned int, Graph = const boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS>, mpl_::true_ = mpl_::bool_<true>]’
/usr/include/boost/graph/visitors.hpp:140:5:   instantiated from ‘void boost::invoke_visitors(Visitor&, T, Graph&, Tag) [with Visitor = boost::time_stamper<__gnu_cxx::__normal_iterator<long unsigned int*, std::vector<long unsigned int> >, long unsigned int, boost::on_discover_vertex>, T = long unsigned int, Graph = const boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS>, Tag = boost::on_discover_vertex]’

Answer 1

stamp_times (and the other EventVisitors) expects a WritablePropertyMap . According to this there are specializations of property_traits that allow using c++ pointers as property maps and according to this "Since the iterator of a std::vector (obtained with a call to begin()) is a pointer, the pointer property map method also works for std::vector::iterator". Apparently this last part is not true with recent versions of g++ (tested on 4.6.3 and 4.7.1). So in order to invoke stamp_times you need to use &dtime[0] instead of dtime.begin() .