williamr@2: //=======================================================================
williamr@2: // Copyright 2002 Indiana University.
williamr@2: // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
williamr@2: //
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: //=======================================================================
williamr@2: 
williamr@2: #ifndef BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP
williamr@2: #define BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP
williamr@2: 
williamr@2: #include <boost/graph/topological_sort.hpp>
williamr@2: #include <boost/graph/dijkstra_shortest_paths.hpp>
williamr@2: 
williamr@2: // single-source shortest paths for a Directed Acyclic Graph (DAG)
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2:   // Initalize distances and call depth first search
williamr@2:   template <class VertexListGraph, class DijkstraVisitor, 
williamr@2:             class DistanceMap, class WeightMap, class ColorMap, 
williamr@2:             class PredecessorMap,
williamr@2:             class Compare, class Combine, 
williamr@2:             class DistInf, class DistZero>
williamr@2:   inline void
williamr@2:   dag_shortest_paths
williamr@2:     (const VertexListGraph& g,
williamr@2:      typename graph_traits<VertexListGraph>::vertex_descriptor s, 
williamr@2:      DistanceMap distance, WeightMap weight, ColorMap color,
williamr@2:      PredecessorMap pred,
williamr@2:      DijkstraVisitor vis, Compare compare, Combine combine, 
williamr@2:      DistInf inf, DistZero zero)
williamr@2:   {
williamr@2:     typedef typename graph_traits<VertexListGraph>::vertex_descriptor Vertex;
williamr@2:     std::vector<Vertex> rev_topo_order;
williamr@2:     rev_topo_order.reserve(num_vertices(g));
williamr@2: 
williamr@2:     // Call 'depth_first_visit', not 'topological_sort', because we don't
williamr@2:     // want to traverse the entire graph, only vertices reachable from 's',
williamr@2:     // and 'topological_sort' will traverse everything. The logic below
williamr@2:     // is the same as for 'topological_sort', only we call 'depth_first_visit'
williamr@2:     // and 'topological_sort' calls 'depth_first_search'.
williamr@2:     topo_sort_visitor<std::back_insert_iterator<std::vector<Vertex> > >
williamr@2:         topo_visitor(std::back_inserter(rev_topo_order));
williamr@2:     depth_first_visit(g, s, topo_visitor, color);
williamr@2: 
williamr@2:     typename graph_traits<VertexListGraph>::vertex_iterator ui, ui_end;
williamr@2:     for (tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui) {
williamr@2:       put(distance, *ui, inf);
williamr@2:       put(pred, *ui, *ui);
williamr@2:     }
williamr@2: 
williamr@2:     put(distance, s, zero);
williamr@2:     vis.discover_vertex(s, g);
williamr@2:     typename std::vector<Vertex>::reverse_iterator i;
williamr@2:     for (i = rev_topo_order.rbegin(); i != rev_topo_order.rend(); ++i) {
williamr@2:       Vertex u = *i;
williamr@2:       vis.examine_vertex(u, g);
williamr@2:       typename graph_traits<VertexListGraph>::out_edge_iterator e, e_end;
williamr@2:       for (tie(e, e_end) = out_edges(u, g); e != e_end; ++e) {
williamr@2:         vis.discover_vertex(target(*e, g), g);
williamr@2:         bool decreased = relax(*e, g, weight, pred, distance, 
williamr@2:                                combine, compare);
williamr@2:         if (decreased)
williamr@2:           vis.edge_relaxed(*e, g);
williamr@2:         else
williamr@2:           vis.edge_not_relaxed(*e, g);
williamr@2:       }
williamr@2:       vis.finish_vertex(u, g);      
williamr@2:     }
williamr@2:   }
williamr@2: 
williamr@2:   namespace detail {
williamr@2: 
williamr@2:     // Defaults are the same as Dijkstra's algorithm
williamr@2: 
williamr@2:     // Handle Distance Compare, Combine, Inf and Zero defaults
williamr@2:     template <class VertexListGraph, class DijkstraVisitor, 
williamr@2:       class DistanceMap, class WeightMap, class ColorMap, 
williamr@2:       class IndexMap, class Params>
williamr@2:     inline void
williamr@2:     dag_sp_dispatch2
williamr@2:       (const VertexListGraph& g,
williamr@2:        typename graph_traits<VertexListGraph>::vertex_descriptor s, 
williamr@2:        DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,
williamr@2:        DijkstraVisitor vis, const Params& params)
williamr@2:     {
williamr@2:       typedef typename property_traits<DistanceMap>::value_type D;
williamr@2:       dummy_property_map p_map;
williamr@2:       dag_shortest_paths
williamr@2:         (g, s, distance, weight, color, 
williamr@2:          choose_param(get_param(params, vertex_predecessor), p_map),
williamr@2:          vis, 
williamr@2:          choose_param(get_param(params, distance_compare_t()), std::less<D>()),
williamr@2:          choose_param(get_param(params, distance_combine_t()), closed_plus<D>()),
williamr@2:          choose_param(get_param(params, distance_inf_t()), 
williamr@2:                       (std::numeric_limits<D>::max)()),
williamr@2:          choose_param(get_param(params, distance_zero_t()), 
williamr@2:                       D()));
williamr@2:     }
williamr@2: 
williamr@2:     // Handle DistanceMap and ColorMap defaults
williamr@2:     template <class VertexListGraph, class DijkstraVisitor, 
williamr@2:               class DistanceMap, class WeightMap, class ColorMap,
williamr@2:               class IndexMap, class Params>
williamr@2:     inline void
williamr@2:     dag_sp_dispatch1
williamr@2:       (const VertexListGraph& g,
williamr@2:        typename graph_traits<VertexListGraph>::vertex_descriptor s, 
williamr@2:        DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,
williamr@2:        DijkstraVisitor vis, const Params& params)
williamr@2:     {
williamr@2:       typedef typename property_traits<WeightMap>::value_type T;
williamr@2:       typename std::vector<T>::size_type n;
williamr@2:       n = is_default_param(distance) ? num_vertices(g) : 1;
williamr@2:       std::vector<T> distance_map(n);
williamr@2:       n = is_default_param(color) ? num_vertices(g) : 1;
williamr@2:       std::vector<default_color_type> color_map(n);
williamr@2: 
williamr@2:       dag_sp_dispatch2
williamr@2:         (g, s, 
williamr@2:          choose_param(distance, 
williamr@2:                       make_iterator_property_map(distance_map.begin(), id,
williamr@2:                                                  distance_map[0])),
williamr@2:          weight, 
williamr@2:          choose_param(color,
williamr@2:                       make_iterator_property_map(color_map.begin(), id, 
williamr@2:                                                  color_map[0])),
williamr@2:          id, vis, params);
williamr@2:     }
williamr@2:     
williamr@2:   } // namespace detail 
williamr@2:   
williamr@2:   template <class VertexListGraph, class Param, class Tag, class Rest>
williamr@2:   inline void
williamr@2:   dag_shortest_paths
williamr@2:     (const VertexListGraph& g,
williamr@2:      typename graph_traits<VertexListGraph>::vertex_descriptor s,
williamr@2:      const bgl_named_params<Param,Tag,Rest>& params)
williamr@2:   {
williamr@2:     // assert that the graph is directed...
williamr@2:     null_visitor null_vis;
williamr@2:     detail::dag_sp_dispatch1
williamr@2:       (g, s, 
williamr@2:        get_param(params, vertex_distance),
williamr@2:        choose_const_pmap(get_param(params, edge_weight), g, edge_weight),
williamr@2:        get_param(params, vertex_color),
williamr@2:        choose_const_pmap(get_param(params, vertex_index), g, vertex_index),
williamr@2:        choose_param(get_param(params, graph_visitor),
williamr@2:                     make_dijkstra_visitor(null_vis)),
williamr@2:        params);
williamr@2:   }
williamr@2:   
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #endif // BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP