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