File: depth_first_search.hpp

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//=======================================================================
// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// Copyright 2003 Bruce Barr
// 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)
//=======================================================================

// Nonrecursive implementation of depth_first_visit_impl submitted by
// Bruce Barr, schmoost <at> yahoo.com, May/June 2003.
#ifndef BOOST_GRAPH_RECURSIVE_DFS_HPP
#define BOOST_GRAPH_RECURSIVE_DFS_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/visitors.hpp>
#include <boost/graph/named_function_params.hpp>
#include <boost/ref.hpp>
#include <boost/implicit_cast.hpp>
#include <boost/optional.hpp>
#include <boost/parameter.hpp>
#include <boost/concept/assert.hpp>
#include <boost/tti/has_member_function.hpp>

#include <vector>
#include <utility>

namespace boost {

  template <class Visitor, class Graph>
  class DFSVisitorConcept {
  public:
    void constraints() {
      BOOST_CONCEPT_ASSERT(( CopyConstructibleConcept<Visitor> ));
      vis.initialize_vertex(u, g);
      vis.start_vertex(u, g);
      vis.discover_vertex(u, g);
      vis.examine_edge(e, g);
      vis.tree_edge(e, g);
      vis.back_edge(e, g);
      vis.forward_or_cross_edge(e, g);
      // vis.finish_edge(e, g); // Optional for user
      vis.finish_vertex(u, g);
    }
  private:
    Visitor vis;
    Graph g;
    typename graph_traits<Graph>::vertex_descriptor u;
    typename graph_traits<Graph>::edge_descriptor e;
  };

  namespace detail {

    struct nontruth2 {
      template<class T, class T2>
      bool operator()(const T&, const T2&) const { return false; }
    };

    BOOST_TTI_HAS_MEMBER_FUNCTION(finish_edge)

    template <bool IsCallable> struct do_call_finish_edge {
      template <typename E, typename G, typename Vis>
      static void call_finish_edge(Vis& vis, E e, const G& g) {
        vis.finish_edge(e, g);
      }
    };

    template <> struct do_call_finish_edge<false> {
      template <typename E, typename G, typename Vis>
      static void call_finish_edge(Vis&, E, const G&) {}
    };

    template <typename E, typename G, typename Vis>
    void call_finish_edge(Vis& vis, E e, const G& g) { // Only call if method exists
#if ((defined(__GNUC__) && (__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 9))) || \
      defined(__clang__) || \
     (defined(__INTEL_COMPILER) && (__INTEL_COMPILER >= 1200)))
      do_call_finish_edge<
        has_member_function_finish_edge<Vis, void,
          boost::mpl::vector<E, const G&> >::value>::call_finish_edge(vis, e, g);
#else
      do_call_finish_edge<has_member_function_finish_edge<Vis, void>::value>::call_finish_edge(vis, e, g);
#endif
    }


// Define BOOST_RECURSIVE_DFS to use older, recursive version.
// It is retained for a while in order to perform performance
// comparison.
#ifndef BOOST_RECURSIVE_DFS

    // If the vertex u and the iterators ei and ei_end are thought of as the
    // context of the algorithm, each push and pop from the stack could
    // be thought of as a context shift.
    // Each pass through "while (ei != ei_end)" may refer to the out-edges of
    // an entirely different vertex, because the context of the algorithm
    // shifts every time a white adjacent vertex is discovered.
    // The corresponding context shift back from the adjacent vertex occurs
    // after all of its out-edges have been examined.
    //
    // See http://lists.boost.org/MailArchives/boost/msg48752.php for FAQ.

    template <class IncidenceGraph, class DFSVisitor, class ColorMap,
            class TerminatorFunc>
    void depth_first_visit_impl
      (const IncidenceGraph& g,
       typename graph_traits<IncidenceGraph>::vertex_descriptor u,
       DFSVisitor& vis,
       ColorMap color, TerminatorFunc func = TerminatorFunc())
    {
      BOOST_CONCEPT_ASSERT(( IncidenceGraphConcept<IncidenceGraph> ));
      BOOST_CONCEPT_ASSERT(( DFSVisitorConcept<DFSVisitor, IncidenceGraph> ));
      typedef typename graph_traits<IncidenceGraph>::vertex_descriptor Vertex;
      typedef typename graph_traits<IncidenceGraph>::edge_descriptor Edge;
      BOOST_CONCEPT_ASSERT(( ReadWritePropertyMapConcept<ColorMap, Vertex> ));
      typedef typename property_traits<ColorMap>::value_type ColorValue;
      BOOST_CONCEPT_ASSERT(( ColorValueConcept<ColorValue> ));
      typedef color_traits<ColorValue> Color;
      typedef typename graph_traits<IncidenceGraph>::out_edge_iterator Iter;
      typedef std::pair<Vertex, std::pair<boost::optional<Edge>, std::pair<Iter, Iter> > > VertexInfo;

      boost::optional<Edge> src_e;
      Iter ei, ei_end;
      std::vector<VertexInfo> stack;

      // Possible optimization for vector
      //stack.reserve(num_vertices(g));

      put(color, u, Color::gray());
      vis.discover_vertex(u, g);
      boost::tie(ei, ei_end) = out_edges(u, g);
      if (func(u, g)) {
          // If this vertex terminates the search, we push empty range
          stack.push_back(std::make_pair(u, std::make_pair(boost::optional<Edge>(), std::make_pair(ei_end, ei_end))));
      } else {
          stack.push_back(std::make_pair(u, std::make_pair(boost::optional<Edge>(), std::make_pair(ei, ei_end))));
      }
      while (!stack.empty()) {
        VertexInfo& back = stack.back();
        u = back.first;
        src_e = back.second.first;
        boost::tie(ei, ei_end) = back.second.second;
        stack.pop_back();
	// finish_edge has to be called here, not after the
	// loop. Think of the pop as the return from a recursive call.
        if (src_e) {
	  call_finish_edge(vis, src_e.get(), g);
	}
        while (ei != ei_end) {
          Vertex v = target(*ei, g);
          vis.examine_edge(*ei, g);
          ColorValue v_color = get(color, v);
          if (v_color == Color::white()) {
            vis.tree_edge(*ei, g);
            src_e = *ei;
            stack.push_back(std::make_pair(u, std::make_pair(src_e, std::make_pair(++ei, ei_end))));
            u = v;
            put(color, u, Color::gray());
            vis.discover_vertex(u, g);
            boost::tie(ei, ei_end) = out_edges(u, g);
            if (func(u, g)) {
                ei = ei_end;
            }
          } else {
            if (v_color == Color::gray()) {
              vis.back_edge(*ei, g);
            } else {
              vis.forward_or_cross_edge(*ei, g);
            }
            call_finish_edge(vis, *ei, g);
            ++ei;
          }
        }
        put(color, u, Color::black());
        vis.finish_vertex(u, g);
      }
    }

#else // BOOST_RECURSIVE_DFS is defined

    template <class IncidenceGraph, class DFSVisitor, class ColorMap,
              class TerminatorFunc>
    void depth_first_visit_impl
      (const IncidenceGraph& g,
       typename graph_traits<IncidenceGraph>::vertex_descriptor u,
       DFSVisitor& vis,  // pass-by-reference here, important!
       ColorMap color, TerminatorFunc func)
    {
      BOOST_CONCEPT_ASSERT(( IncidenceGraphConcept<IncidenceGraph> ));
      BOOST_CONCEPT_ASSERT(( DFSVisitorConcept<DFSVisitor, IncidenceGraph> ));
      typedef typename graph_traits<IncidenceGraph>::vertex_descriptor Vertex;
      BOOST_CONCEPT_ASSERT(( ReadWritePropertyMapConcept<ColorMap, Vertex> ));
      typedef typename property_traits<ColorMap>::value_type ColorValue;
      BOOST_CONCEPT_ASSERT(( ColorValueConcept<ColorValue> ));
      typedef color_traits<ColorValue> Color;
      typename graph_traits<IncidenceGraph>::out_edge_iterator ei, ei_end;

      put(color, u, Color::gray());          vis.discover_vertex(u, g);

      if (!func(u, g))
        for (boost::tie(ei, ei_end) = out_edges(u, g); ei != ei_end; ++ei) {
          Vertex v = target(*ei, g);           vis.examine_edge(*ei, g);
          ColorValue v_color = get(color, v);
          if (v_color == Color::white()) {     vis.tree_edge(*ei, g);
          depth_first_visit_impl(g, v, vis, color, func);
          } else if (v_color == Color::gray()) vis.back_edge(*ei, g);
          else                                 vis.forward_or_cross_edge(*ei, g);
          call_finish_edge(vis, *ei, g);
        }
      put(color, u, Color::black());         vis.finish_vertex(u, g);
    }

#endif

  } // namespace detail

  template <class VertexListGraph, class DFSVisitor, class ColorMap>
  void
  depth_first_search(const VertexListGraph& g, DFSVisitor vis, ColorMap color,
                     typename graph_traits<VertexListGraph>::vertex_descriptor start_vertex)
  {
    typedef typename graph_traits<VertexListGraph>::vertex_descriptor Vertex;
    BOOST_CONCEPT_ASSERT(( DFSVisitorConcept<DFSVisitor, VertexListGraph> ));
    typedef typename property_traits<ColorMap>::value_type ColorValue;
    typedef color_traits<ColorValue> Color;

    typename graph_traits<VertexListGraph>::vertex_iterator ui, ui_end;
    for (boost::tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui) {
      Vertex u = implicit_cast<Vertex>(*ui);
      put(color, u, Color::white()); vis.initialize_vertex(u, g);
    }

    if (start_vertex != detail::get_default_starting_vertex(g)){ vis.start_vertex(start_vertex, g);
      detail::depth_first_visit_impl(g, start_vertex, vis, color,
                                     detail::nontruth2());
    }

    for (boost::tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui) {
      Vertex u = implicit_cast<Vertex>(*ui);
      ColorValue u_color = get(color, u);
      if (u_color == Color::white()) {       vis.start_vertex(u, g);
        detail::depth_first_visit_impl(g, u, vis, color, detail::nontruth2());
      }
    }
  }

  template <class VertexListGraph, class DFSVisitor, class ColorMap>
  void
  depth_first_search(const VertexListGraph& g, DFSVisitor vis, ColorMap color)
  {
    typedef typename boost::graph_traits<VertexListGraph>::vertex_iterator vi;
    std::pair<vi, vi> verts = vertices(g);
    if (verts.first == verts.second)
      return;

    depth_first_search(g, vis, color, detail::get_default_starting_vertex(g));
  }

  template <class Visitors = null_visitor>
  class dfs_visitor {
  public:
    dfs_visitor() { }
    dfs_visitor(Visitors vis) : m_vis(vis) { }

    template <class Vertex, class Graph>
    void initialize_vertex(Vertex u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_initialize_vertex());
    }
    template <class Vertex, class Graph>
    void start_vertex(Vertex u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_start_vertex());
    }
    template <class Vertex, class Graph>
    void discover_vertex(Vertex u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_discover_vertex());
    }
    template <class Edge, class Graph>
    void examine_edge(Edge u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_examine_edge());
    }
    template <class Edge, class Graph>
    void tree_edge(Edge u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_tree_edge());
    }
    template <class Edge, class Graph>
    void back_edge(Edge u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_back_edge());
    }
    template <class Edge, class Graph>
    void forward_or_cross_edge(Edge u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_forward_or_cross_edge());
    }
    template <class Edge, class Graph>
    void finish_edge(Edge u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_finish_edge());
    }
    template <class Vertex, class Graph>
    void finish_vertex(Vertex u, const Graph& g) {
      invoke_visitors(m_vis, u, g, ::boost::on_finish_vertex());
    }

    BOOST_GRAPH_EVENT_STUB(on_initialize_vertex,dfs)
    BOOST_GRAPH_EVENT_STUB(on_start_vertex,dfs)
    BOOST_GRAPH_EVENT_STUB(on_discover_vertex,dfs)
    BOOST_GRAPH_EVENT_STUB(on_examine_edge,dfs)
    BOOST_GRAPH_EVENT_STUB(on_tree_edge,dfs)
    BOOST_GRAPH_EVENT_STUB(on_back_edge,dfs)
    BOOST_GRAPH_EVENT_STUB(on_forward_or_cross_edge,dfs)
    BOOST_GRAPH_EVENT_STUB(on_finish_edge,dfs)
    BOOST_GRAPH_EVENT_STUB(on_finish_vertex,dfs)

  protected:
    Visitors m_vis;
  };
  template <class Visitors>
  dfs_visitor<Visitors>
  make_dfs_visitor(Visitors vis) {
    return dfs_visitor<Visitors>(vis);
  }
  typedef dfs_visitor<> default_dfs_visitor;

  // Boost.Parameter named parameter variant
  namespace graph {
    namespace detail {
      template <typename Graph>
      struct depth_first_search_impl {
        typedef void result_type;
        template <typename ArgPack>
        void operator()(const Graph& g, const ArgPack& arg_pack) const {
          using namespace boost::graph::keywords;
          boost::depth_first_search(g,
                                    arg_pack[_visitor | make_dfs_visitor(null_visitor())],
                                    boost::detail::make_color_map_from_arg_pack(g, arg_pack),
                                    arg_pack[_root_vertex || boost::detail::get_default_starting_vertex_t<Graph>(g)]);
        }
      };
    }
    BOOST_GRAPH_MAKE_FORWARDING_FUNCTION(depth_first_search, 1, 4)
  }

  BOOST_GRAPH_MAKE_OLD_STYLE_PARAMETER_FUNCTION(depth_first_search, 1)

  template <class IncidenceGraph, class DFSVisitor, class ColorMap>
  void depth_first_visit
    (const IncidenceGraph& g,
     typename graph_traits<IncidenceGraph>::vertex_descriptor u,
     DFSVisitor vis, ColorMap color)
  {
    vis.start_vertex(u, g);
    detail::depth_first_visit_impl(g, u, vis, color, detail::nontruth2());
  }

  template <class IncidenceGraph, class DFSVisitor, class ColorMap,
            class TerminatorFunc>
  void depth_first_visit
    (const IncidenceGraph& g,
     typename graph_traits<IncidenceGraph>::vertex_descriptor u,
     DFSVisitor vis, ColorMap color, TerminatorFunc func = TerminatorFunc())
  {
    vis.start_vertex(u, g);
    detail::depth_first_visit_impl(g, u, vis, color, func);
  }
} // namespace boost

#ifdef BOOST_GRAPH_USE_MPI
#  include <boost/graph/distributed/depth_first_search.hpp>
#endif

#endif