boost/graph/bellman_ford_shortest_paths.hpp
// //======================================================================= // Copyright 1997, 1998, 1999, 2000 University of Notre Dame. // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) //======================================================================= // /* This file implements the function template <class EdgeListGraph, class Size, class P, class T, class R> bool bellman_ford_shortest_paths(EdgeListGraph& g, Size N, const bgl_named_params<P, T, R>& params) */ #ifndef BOOST_GRAPH_BELLMAN_FORD_SHORTEST_PATHS_HPP #define BOOST_GRAPH_BELLMAN_FORD_SHORTEST_PATHS_HPP #include <boost/config.hpp> #include <boost/graph/graph_traits.hpp> #include <boost/graph/graph_concepts.hpp> #include <boost/graph/properties.hpp> #include <boost/graph/relax.hpp> #include <boost/graph/visitors.hpp> #include <boost/graph/named_function_params.hpp> #include <boost/concept/assert.hpp> namespace boost { template < class Visitor, class Graph > struct BellmanFordVisitorConcept { void constraints() { BOOST_CONCEPT_ASSERT((CopyConstructibleConcept< Visitor >)); vis.examine_edge(e, g); vis.edge_relaxed(e, g); vis.edge_not_relaxed(e, g); vis.edge_minimized(e, g); vis.edge_not_minimized(e, g); } Visitor vis; Graph g; typename graph_traits< Graph >::edge_descriptor e; }; template < class Visitors = null_visitor > class bellman_visitor { public: bellman_visitor() {} bellman_visitor(Visitors vis) : m_vis(vis) {} template < class Edge, class Graph > void examine_edge(Edge u, Graph& g) { invoke_visitors(m_vis, u, g, on_examine_edge()); } template < class Edge, class Graph > void edge_relaxed(Edge u, Graph& g) { invoke_visitors(m_vis, u, g, on_edge_relaxed()); } template < class Edge, class Graph > void edge_not_relaxed(Edge u, Graph& g) { invoke_visitors(m_vis, u, g, on_edge_not_relaxed()); } template < class Edge, class Graph > void edge_minimized(Edge u, Graph& g) { invoke_visitors(m_vis, u, g, on_edge_minimized()); } template < class Edge, class Graph > void edge_not_minimized(Edge u, Graph& g) { invoke_visitors(m_vis, u, g, on_edge_not_minimized()); } protected: Visitors m_vis; }; template < class Visitors > bellman_visitor< Visitors > make_bellman_visitor(Visitors vis) { return bellman_visitor< Visitors >(vis); } typedef bellman_visitor<> default_bellman_visitor; template < class EdgeListGraph, class Size, class WeightMap, class PredecessorMap, class DistanceMap, class BinaryFunction, class BinaryPredicate, class BellmanFordVisitor > bool bellman_ford_shortest_paths(EdgeListGraph& g, Size N, WeightMap weight, PredecessorMap pred, DistanceMap distance, BinaryFunction combine, BinaryPredicate compare, BellmanFordVisitor v) { BOOST_CONCEPT_ASSERT((EdgeListGraphConcept< EdgeListGraph >)); typedef graph_traits< EdgeListGraph > GTraits; typedef typename GTraits::edge_descriptor Edge; typedef typename GTraits::vertex_descriptor Vertex; BOOST_CONCEPT_ASSERT((ReadWritePropertyMapConcept< DistanceMap, Vertex >)); BOOST_CONCEPT_ASSERT((ReadablePropertyMapConcept< WeightMap, Edge >)); typename GTraits::edge_iterator i, end; for (Size k = 0; k < N; ++k) { bool at_least_one_edge_relaxed = false; for (boost::tie(i, end) = edges(g); i != end; ++i) { v.examine_edge(*i, g); if (relax(*i, g, weight, pred, distance, combine, compare)) { at_least_one_edge_relaxed = true; v.edge_relaxed(*i, g); } else v.edge_not_relaxed(*i, g); } if (!at_least_one_edge_relaxed) break; } for (boost::tie(i, end) = edges(g); i != end; ++i) if (compare(combine(get(distance, source(*i, g)), get(weight, *i)), get(distance, target(*i, g)))) { v.edge_not_minimized(*i, g); return false; } else v.edge_minimized(*i, g); return true; } namespace detail { template < typename VertexAndEdgeListGraph, typename Size, typename WeightMap, typename PredecessorMap, typename DistanceMap, typename P, typename T, typename R > bool bellman_dispatch2(VertexAndEdgeListGraph& g, typename graph_traits< VertexAndEdgeListGraph >::vertex_descriptor s, Size N, WeightMap weight, PredecessorMap pred, DistanceMap distance, const bgl_named_params< P, T, R >& params) { typedef typename property_traits< DistanceMap >::value_type D; bellman_visitor<> null_vis; typedef typename property_traits< WeightMap >::value_type weight_type; typename graph_traits< VertexAndEdgeListGraph >::vertex_iterator v, v_end; for (boost::tie(v, v_end) = vertices(g); v != v_end; ++v) { put(distance, *v, (std::numeric_limits< weight_type >::max)()); put(pred, *v, *v); } put(distance, s, weight_type(0)); return bellman_ford_shortest_paths(g, N, weight, pred, distance, choose_param( get_param(params, distance_combine_t()), closed_plus< D >()), choose_param( get_param(params, distance_compare_t()), std::less< D >()), choose_param(get_param(params, graph_visitor), null_vis)); } template < typename VertexAndEdgeListGraph, typename Size, typename WeightMap, typename PredecessorMap, typename DistanceMap, typename P, typename T, typename R > bool bellman_dispatch2(VertexAndEdgeListGraph& g, param_not_found, Size N, WeightMap weight, PredecessorMap pred, DistanceMap distance, const bgl_named_params< P, T, R >& params) { typedef typename property_traits< DistanceMap >::value_type D; bellman_visitor<> null_vis; return bellman_ford_shortest_paths(g, N, weight, pred, distance, choose_param( get_param(params, distance_combine_t()), closed_plus< D >()), choose_param( get_param(params, distance_compare_t()), std::less< D >()), choose_param(get_param(params, graph_visitor), null_vis)); } template < class EdgeListGraph, class Size, class WeightMap, class DistanceMap, class P, class T, class R > bool bellman_dispatch(EdgeListGraph& g, Size N, WeightMap weight, DistanceMap distance, const bgl_named_params< P, T, R >& params) { dummy_property_map dummy_pred; return detail::bellman_dispatch2(g, get_param(params, root_vertex_t()), N, weight, choose_param(get_param(params, vertex_predecessor), dummy_pred), distance, params); } } // namespace detail template < class EdgeListGraph, class Size, class P, class T, class R > bool bellman_ford_shortest_paths( EdgeListGraph& g, Size N, const bgl_named_params< P, T, R >& params) { return detail::bellman_dispatch(g, N, choose_const_pmap(get_param(params, edge_weight), g, edge_weight), choose_pmap(get_param(params, vertex_distance), g, vertex_distance), params); } template < class EdgeListGraph, class Size > bool bellman_ford_shortest_paths(EdgeListGraph& g, Size N) { bgl_named_params< int, int > params(0); return bellman_ford_shortest_paths(g, N, params); } template < class VertexAndEdgeListGraph, class P, class T, class R > bool bellman_ford_shortest_paths( VertexAndEdgeListGraph& g, const bgl_named_params< P, T, R >& params) { BOOST_CONCEPT_ASSERT((VertexListGraphConcept< VertexAndEdgeListGraph >)); return detail::bellman_dispatch(g, num_vertices(g), choose_const_pmap(get_param(params, edge_weight), g, edge_weight), choose_pmap(get_param(params, vertex_distance), g, vertex_distance), params); } } // namespace boost #endif // BOOST_GRAPH_BELLMAN_FORD_SHORTEST_PATHS_HPP