Chris@16: //=======================================================================
Chris@16: // Copyright 2002 Indiana University.
Chris@16: // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //=======================================================================
Chris@16: 
Chris@16: #ifndef BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP
Chris@16: #define BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP
Chris@16: 
Chris@16: #include <boost/graph/topological_sort.hpp>
Chris@16: #include <boost/graph/dijkstra_shortest_paths.hpp>
Chris@16: 
Chris@16: // single-source shortest paths for a Directed Acyclic Graph (DAG)
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16:   // Initalize distances and call depth first search
Chris@16:   template <class VertexListGraph, class DijkstraVisitor, 
Chris@16:             class DistanceMap, class WeightMap, class ColorMap, 
Chris@16:             class PredecessorMap,
Chris@16:             class Compare, class Combine, 
Chris@16:             class DistInf, class DistZero>
Chris@16:   inline void
Chris@16:   dag_shortest_paths
Chris@16:     (const VertexListGraph& g,
Chris@16:      typename graph_traits<VertexListGraph>::vertex_descriptor s, 
Chris@16:      DistanceMap distance, WeightMap weight, ColorMap color,
Chris@16:      PredecessorMap pred,
Chris@16:      DijkstraVisitor vis, Compare compare, Combine combine, 
Chris@16:      DistInf inf, DistZero zero)
Chris@16:   {
Chris@16:     typedef typename graph_traits<VertexListGraph>::vertex_descriptor Vertex;
Chris@16:     std::vector<Vertex> rev_topo_order;
Chris@16:     rev_topo_order.reserve(num_vertices(g));
Chris@16: 
Chris@16:     // Call 'depth_first_visit', not 'topological_sort', because we don't
Chris@16:     // want to traverse the entire graph, only vertices reachable from 's',
Chris@16:     // and 'topological_sort' will traverse everything. The logic below
Chris@16:     // is the same as for 'topological_sort', only we call 'depth_first_visit'
Chris@16:     // and 'topological_sort' calls 'depth_first_search'.
Chris@16:     topo_sort_visitor<std::back_insert_iterator<std::vector<Vertex> > >
Chris@16:         topo_visitor(std::back_inserter(rev_topo_order));
Chris@16:     depth_first_visit(g, s, topo_visitor, color);
Chris@16: 
Chris@16:     typename graph_traits<VertexListGraph>::vertex_iterator ui, ui_end;
Chris@16:     for (boost::tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui) {
Chris@16:       put(distance, *ui, inf);
Chris@16:       put(pred, *ui, *ui);
Chris@16:     }
Chris@16: 
Chris@16:     put(distance, s, zero);
Chris@16:     vis.discover_vertex(s, g);
Chris@16:     typename std::vector<Vertex>::reverse_iterator i;
Chris@16:     for (i = rev_topo_order.rbegin(); i != rev_topo_order.rend(); ++i) {
Chris@16:       Vertex u = *i;
Chris@16:       vis.examine_vertex(u, g);
Chris@16:       typename graph_traits<VertexListGraph>::out_edge_iterator e, e_end;
Chris@16:       for (boost::tie(e, e_end) = out_edges(u, g); e != e_end; ++e) {
Chris@16:         vis.discover_vertex(target(*e, g), g);
Chris@16:         bool decreased = relax(*e, g, weight, pred, distance, 
Chris@16:                                combine, compare);
Chris@16:         if (decreased)
Chris@16:           vis.edge_relaxed(*e, g);
Chris@16:         else
Chris@16:           vis.edge_not_relaxed(*e, g);
Chris@16:       }
Chris@16:       vis.finish_vertex(u, g);      
Chris@16:     }
Chris@16:   }
Chris@16: 
Chris@16:   namespace detail {
Chris@16: 
Chris@16:     // Defaults are the same as Dijkstra's algorithm
Chris@16: 
Chris@16:     // Handle Distance Compare, Combine, Inf and Zero defaults
Chris@16:     template <class VertexListGraph, class DijkstraVisitor, 
Chris@16:       class DistanceMap, class WeightMap, class ColorMap, 
Chris@16:       class IndexMap, class Params>
Chris@16:     inline void
Chris@16:     dag_sp_dispatch2
Chris@16:       (const VertexListGraph& g,
Chris@16:        typename graph_traits<VertexListGraph>::vertex_descriptor s, 
Chris@16:        DistanceMap distance, WeightMap weight, ColorMap color, IndexMap /*id*/,
Chris@16:        DijkstraVisitor vis, const Params& params)
Chris@16:     {
Chris@16:       typedef typename property_traits<DistanceMap>::value_type D;
Chris@16:       dummy_property_map p_map;
Chris@16:       D inf =
Chris@16:         choose_param(get_param(params, distance_inf_t()), 
Chris@16:                      (std::numeric_limits<D>::max)());
Chris@16:       dag_shortest_paths
Chris@16:         (g, s, distance, weight, color, 
Chris@16:          choose_param(get_param(params, vertex_predecessor), p_map),
Chris@16:          vis, 
Chris@16:          choose_param(get_param(params, distance_compare_t()), std::less<D>()),
Chris@16:          choose_param(get_param(params, distance_combine_t()), closed_plus<D>(inf)),
Chris@16:          inf,
Chris@16:          choose_param(get_param(params, distance_zero_t()), 
Chris@16:                       D()));
Chris@16:     }
Chris@16: 
Chris@16:     // Handle DistanceMap and ColorMap defaults
Chris@16:     template <class VertexListGraph, class DijkstraVisitor, 
Chris@16:               class DistanceMap, class WeightMap, class ColorMap,
Chris@16:               class IndexMap, class Params>
Chris@16:     inline void
Chris@16:     dag_sp_dispatch1
Chris@16:       (const VertexListGraph& g,
Chris@16:        typename graph_traits<VertexListGraph>::vertex_descriptor s, 
Chris@16:        DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,
Chris@16:        DijkstraVisitor vis, const Params& params)
Chris@16:     {
Chris@16:       typedef typename property_traits<WeightMap>::value_type T;
Chris@16:       typename std::vector<T>::size_type n;
Chris@16:       n = is_default_param(distance) ? num_vertices(g) : 1;
Chris@16:       std::vector<T> distance_map(n);
Chris@16:       n = is_default_param(color) ? num_vertices(g) : 1;
Chris@16:       std::vector<default_color_type> color_map(n);
Chris@16: 
Chris@16:       dag_sp_dispatch2
Chris@16:         (g, s, 
Chris@16:          choose_param(distance, 
Chris@16:                       make_iterator_property_map(distance_map.begin(), id,
Chris@16:                                                  distance_map[0])),
Chris@16:          weight, 
Chris@16:          choose_param(color,
Chris@16:                       make_iterator_property_map(color_map.begin(), id, 
Chris@16:                                                  color_map[0])),
Chris@16:          id, vis, params);
Chris@16:     }
Chris@16:     
Chris@16:   } // namespace detail 
Chris@16:   
Chris@16:   template <class VertexListGraph, class Param, class Tag, class Rest>
Chris@16:   inline void
Chris@16:   dag_shortest_paths
Chris@16:     (const VertexListGraph& g,
Chris@16:      typename graph_traits<VertexListGraph>::vertex_descriptor s,
Chris@16:      const bgl_named_params<Param,Tag,Rest>& params)
Chris@16:   {
Chris@16:     // assert that the graph is directed...
Chris@16:     null_visitor null_vis;
Chris@16:     detail::dag_sp_dispatch1
Chris@16:       (g, s, 
Chris@16:        get_param(params, vertex_distance),
Chris@16:        choose_const_pmap(get_param(params, edge_weight), g, edge_weight),
Chris@16:        get_param(params, vertex_color),
Chris@16:        choose_const_pmap(get_param(params, vertex_index), g, vertex_index),
Chris@16:        choose_param(get_param(params, graph_visitor),
Chris@16:                     make_dijkstra_visitor(null_vis)),
Chris@16:        params);
Chris@16:   }
Chris@16:   
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP