BGL dijkstra_shortest_path algorithm method does n

问题:

I have been trying to get boost graph lib's dijkstra_shortest_paths to compile for about a week now without avail. I am trying to use exterior property maps for the different named parameters required by the templated method. My graph uses bundled properties for the vertex and the edges and I have been able to build the graph successfully. I will show you what I have for the code:

// vertex bundled properties
struct BusStop
{
    unsigned int id; //used for creating vertex index property map
    string name;
    Location* pLocation;
};

// edge bundled properties:
struct Route
{
    string routeName;
    BusType type;
    float distance; 
};

Here is my graph declaration:

typedef boost::adjacency_list<boost::vecS, boost::setS, boost::undirectedS, BusStop, Route> BusRouteGraph;

Here is my method that tries to do dijkstra's shortest path on the given graph:

template<typename Graph>
bool shortestPathSearch(Graph& g, typename   
  boost::graph_traits<Graph>::vertex_descriptor src,
  typename boost::graph_traits<Graph>::vertex_descriptor dest)
{
    bool bPathFound = false;
    VertexIndexMap index_map = get(&BusStop::id, g);

    // Initialize index_map
    typedef typename graph_traits<Graph>::vertex_iterator V_Iter;
    V_Iter v_iter, v_iter_end;
    int c = 0;
    for( boost::tie(v_iter, v_iter_end) = vertices(g); v_iter != v_iter_end; 
         ++v_iter, ++c)
    {
    index_map[*v_iter] = c;
    }

    // Create exterior properties for these
    vector<int> predecessor(num_vertices(g));
    vector<float> distances(num_vertices(g), 0.0f);
    vector<default_color_type> colors(num_vertices(g));

    dijkstra_shortest_paths(g, src, weight_map(get(&Route::distance, g))
    .color_map (make_iterator_property_map(colors.begin(), index_map))
        .distance_map(make_iterator_property_map(distances.begin(), 
                           index_map)));


    return bPathFound;
}

I get these compile time errors:(only the first error below)

\src\BusRouteFinder.cpp:461:2:   instantiated from 'bool shortestPathSearch  (Graph&, typename boost::graph_traits<Graph>::vertex_descriptor, typename boost::graph_traits<Graph>::vertex_descriptor) [with Graph = boost::adjacency_list<boost::vecS, boost::setS, boost::undirectedS, BusStop, Route>, typename boost::graph_traits<Graph>::vertex_descriptor = void*]'
..\src\BusRouteFinder.cpp:91:39:   instantiated from here
C:\boost\boost_1_48_0/boost/graph/two_bit_color_map.hpp:86:3: error: invalid cast from type 'boost::default_property_traits<boost::adj_list_vertex_property_map<boost::adjacency_list<boost::vecS, boost::setS, boost::undirectedS, BusStop, Route>, boost::detail::error_property_not_found, const boost::detail::error_property_not_found&, boost::vertex_index_t> >::value_type {aka boost::detail::error_property_not_found}' to type 'std::size_t {aka unsigned int}'
C:\boost\boost_1_48_0/boost/graph/two_bit_color_map.hpp:88:30: error: no match for 'operator/' in 'i / elements_per_char'
C:\boost\boost_1_48_0/boost/graph/two_bit_color_map.hpp:88:30: note: candidates are:
C:\boost\boost_1_48_0/boost/concept_archetype.hpp:316:3: note: template<class Base> boost::dividable_archetype<Base> boost::operator/(const boost::dividable_archetype<Base>&, const boost::dividable_archetype<Base>&)
C:\boost\boost_1_48_0/boost/concept_archetype.hpp:344:3: note: template<class Return, class BaseFirst, class BaseSecond> Return boost::operator/(const boost::divide_op_first_archetype<Return, BaseFirst>&, const boost::divide_op_second_archetype<Return, BaseSecond>&)
C:\boost\boost_1_48_0/boost/graph/two_bit_color_map.hpp:89:58: error: no match for 'operator%' in 'i % elements_per_char'
C:\boost\boost_1_48_0/boost/graph/two_bit_color_map.hpp:89:58: note: candidates are:
C:\boost\boost_1_48_0/boost/concept_archetype.hpp:317:3: note: template<class Base> boost::modable_archetype<Base> boost::operator%(const boost::modable_archetype<Base>&, const boost::modable_archetype<Base>&)
C:\boost\boost_1_48_0/boost/concept_archetype.hpp:346:3: note: template<class Return, class BaseFirst, class BaseSecond> Return boost::operator%(const boost::mod_op_first_archetype<Return, BaseFirst>&, const boost::mod_op_second_archetype<Return, BaseSecond>&)

I have toiled with this for a long time and I don't seem to be arriving at a solution. I thought I'd ask some one here before I give up on BGL :(

Thanks

回答1:

The error message says that compiler does not find proper vertex_index_t property - a critical element for all search algorithms from Boost.Graph. It is not enough to define a class VertexIndexMap, you also have to tell Boost that this is your "vertex_index".

You can try to add declarations similar to following:

class VertexIndexMap //maps vertex to index
{
public:
    typedef boost::readable_property_map_tag category; 
    typedef size_t  value_type;
    typedef value_type reference;
    typedef BusRouteGraph::vertex_descriptor key_type; 

    VertexIndexMap(const BusRouteGraph& g): _g(&g) {} 

    const BusRouteGraph * _g;
};

namespace boost {

template<>
struct property_map<BusRouteGraph, vertex_index_t > {
    typedef VertexIndexMap const_type;
    //typedef type const_type ; //-- we do not define type as "vertex_index_t" map is read-only 
};

VertexIndexMap get(boost::vertex_index_t, const BusRouteGraph & g )
{
    return VertexIndexMap(g);
}

VertexIndexMap::value_type get(VertexIndexMap map, VertexIndexMap::key_type vertex)
{
    return (*map._g)[vertex].id;
}

} //namespace boost

After that you can drop the loop which inits the index_map; instead we use standard "Boost-ish" way to get the index map

VertexIndexMap index_map = get(boost::vertex_index, g); ///replaces get(&BusStop::id, g);

Then everything should work OK.

Good luck!