text: //  (C) Copyright Jeremy Siek 2004
  //  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)
  
  #include <set>
  
  #include <boost/core/lightweight_test.hpp>
  
  #include <boost/graph/subgraph.hpp>
  #include <boost/graph/adjacency_list.hpp>
  #include <boost/graph/random.hpp>
  #include "graph_test.hpp"
  #include <boost/graph/iteration_macros.hpp>
  #include <boost/random/mersenne_twister.hpp>
  
  #include "test_graph.hpp"
  
  // UNDER CONSTRUCTION
  
  // This is a helper function to recusively compare two subgraphs,
  // including the index for every local edges and their children.
  template < typename subgraph_t >
  void sub_cmp(subgraph_t const& g1, subgraph_t const& g2)
  {
      BOOST_TEST(g1.is_root() == g2.is_root());
      BOOST_TEST(num_vertices(g1) == num_vertices(g2));
      BOOST_TEST(num_edges(g1) == num_edges(g2));
      typename subgraph_t::edge_iterator e1_i, e1_i_end, e2_i, e2_i_end;
      boost::tie(e1_i, e1_i_end) = edges(g1);
      boost::tie(e2_i, e2_i_end) = edges(g2);
      for (; e1_i != e1_i_end; ++e1_i, ++e2_i)
      {
          BOOST_TEST(get(boost::edge_index, g1, *e1_i)
              == get(boost::edge_index, g2, *e2_i));
      }
      typename subgraph_t::const_children_iterator g1_i, g1_i_end, g2_i, g2_i_end;
      boost::tie(g1_i, g1_i_end) = g1.children();
      boost::tie(g2_i, g2_i_end) = g2.children();
      for (; g1_i != g1_i_end && g2_i != g2_i_end; ++g1_i, ++g2_i)
      {
          sub_cmp(*g1_i, *g2_i);
      }
      BOOST_TEST(g1_i == g1_i_end && g2_i == g2_i_end);
  }
  
  int main(int, char*[])
  {
      using namespace boost;
      typedef adjacency_list< vecS, vecS, bidirectionalS,
          property< vertex_color_t, int >,
          property< edge_index_t, std::size_t, property< edge_weight_t, int > > >
          graph_t;
      typedef subgraph< graph_t > subgraph_t;
      typedef graph_traits< subgraph_t >::vertex_descriptor vertex_t;
  
      mt19937 gen;
      for (int t = 0; t < 100; t += 5)
      {
          subgraph_t g;
          int N = t + 2;
          std::vector< vertex_t > vertex_set;
          std::vector< std::pair< vertex_t, vertex_t > > edge_set;
          generate_random_graph(g, N, N * 2, gen, std::back_inserter(vertex_set),
              std::back_inserter(edge_set));
  
          graph_test< subgraph_t > gt;
  
          gt.test_incidence_graph(vertex_set, edge_set, g);
          gt.test_bidirectional_graph(vertex_set, edge_set, g);
          gt.test_adjacency_graph(vertex_set, edge_set, g);
          gt.test_vertex_list_graph(vertex_set, g);
          gt.test_edge_list_graph(vertex_set, edge_set, g);
          gt.test_adjacency_matrix(vertex_set, edge_set, g);
  
          std::vector< vertex_t > sub_vertex_set;
          std::vector< vertex_t > sub_global_map;
          std::vector< vertex_t > global_sub_map(num_vertices(g));
          std::vector< std::pair< vertex_t, vertex_t > > sub_edge_set;
  
          subgraph_t& g_s = g.create_subgraph();
  
          const std::set< vertex_t >::size_type Nsub = N / 2;
  
          // Collect a set of random vertices to put in the subgraph
          std::set< vertex_t > verts;
          while (verts.size() < Nsub)
              verts.insert(random_vertex(g, gen));
  
          for (std::set< vertex_t >::iterator it = verts.begin();
               it != verts.end(); ++it)
          {
              vertex_t v_global = *it;
              vertex_t v = add_vertex(v_global, g_s);
              sub_vertex_set.push_back(v);
              sub_global_map.push_back(v_global);
              global_sub_map[v_global] = v;
          }
  
          // compute induced edges
          BGL_FORALL_EDGES(e, g, subgraph_t)
          if (container_contains(sub_global_map, source(e, g))
              && container_contains(sub_global_map, target(e, g)))
              sub_edge_set.push_back(std::make_pair(
                  global_sub_map[source(e, g)], global_sub_map[target(e, g)]));
  
          gt.test_incidence_graph(sub_vertex_set, sub_edge_set, g_s);
          gt.test_bidirectional_graph(sub_vertex_set, sub_edge_set, g_s);
          gt.test_adjacency_graph(sub_vertex_set, sub_edge_set, g_s);
          gt.test_vertex_list_graph(sub_vertex_set, g_s);
          gt.test_edge_list_graph(sub_vertex_set, sub_edge_set, g_s);
          gt.test_adjacency_matrix(sub_vertex_set, sub_edge_set, g_s);
  
          if (num_vertices(g_s) == 0)
              return 0;
          std::vector< int > weights;
          for (unsigned i = 0; i < num_vertices(g_s); ++i)
              weights.push_back(i * 2);
          gt.test_vertex_property_graph(weights, vertex_color_t(), g_s);
  
          // A regression test: the copy constructor of subgraph did not
          // copy one of the members, so local_edge->global_edge mapping
          // was broken.
          {
              subgraph_t g;
              graph_t::vertex_descriptor v1, v2;
              v1 = add_vertex(g);
              v2 = add_vertex(g);
              add_edge(v1, v2, g);
  
              subgraph_t sub
                  = g.create_subgraph(vertices(g).first, vertices(g).second);
  
              graph_t::edge_iterator ei, ee;
              for (boost::tie(ei, ee) = edges(sub); ei != ee; ++ei)
              {
                  // This used to segfault.
                  get(edge_weight, sub, *ei);
              }
          }
  
          // This block generates a complete graph with 8 vertices,
          // and puts the first and last four of the vertices into two children.
          // Do these again to the children, so there are 4 grandchildren with 2
          // vertices for each. Use the copy constructor to generate a copy and
          // compare with the original one.
          {
              subgraph_t g1;
  
              for (size_t i = 0; i < 8; i++)
              {
                  add_vertex(g1);
              }
              subgraph_t::vertex_iterator vi_start, vi, vi_end, vj_start, vj,
                  vj_end;
              for (tie(vi, vi_end) = vertices(g1); vi != vi_end; ++vi)
              {
                  for (tie(vj, vj_end) = vertices(g1); vj != vj_end; ++vj)
                  {
                      if (*vi != *vj)
                      {
                          add_edge(*vi, *vj, g1);
                      }
                  }
              }
              tie(vi_start, vi_end) = vertices(g1);
              vi = vi_start;
              for (size_t i = 0; i < 4; i++)
              {
                  ++vi;
              }
              g1.create_subgraph(vi_start, vi);
              g1.create_subgraph(++vi, vi_end);
              subgraph_t::children_iterator gi1, gi2;
              gi2 = g1.children().first;
              gi1 = gi2++;
              tie(vi_start, vi_end) = vertices(*gi1);
              vi = vi_start;
              tie(vj_start, vj_end) = vertices(*gi2);
              vj = vj_start;
              for (size_t i = 0; i < 2; i++)
              {
                  ++vi;
                  ++vj;
              }
              (*gi1).create_subgraph(vi_start, vi);
              (*gi1).create_subgraph(++vi, vi_end);
              (*gi2).create_subgraph(vj_start, vj);
              (*gi2).create_subgraph(++vj, vj_end);
              subgraph_t g2(g1);
              sub_cmp(g1, g2);
          }
  
          // Bootstrap the test_graph framework.
          // TODO: Subgraph is fundamentally broken for property types.
          // TODO: Under construction.
          {
              using namespace boost;
              typedef property< edge_index_t, size_t, EdgeBundle > EdgeProp;
              typedef adjacency_list< vecS, vecS, directedS, VertexBundle,
                  EdgeProp >
                  BaseGraph;
              typedef subgraph< BaseGraph > Graph;
              typedef graph_traits< Graph >::vertex_descriptor Vertex;
              Graph g;
              Vertex v = add_vertex(g);
  
              typedef property_map< Graph, int VertexBundle::* >::type BundleMap;
              BundleMap map = get(&VertexBundle::value, g);
              get(map, v);
              //         put(map, v, 5);
              //         BOOST_ASSERT(get(map, v) == 5);
  
              //         test_graph(g);
              return boost::report_errors();
          }
      }
      return boost::report_errors();
  }
  