epoc32/include/stdapis/boost/graph/edge_connectivity.hpp
author William Roberts <williamr@symbian.org>
Wed, 31 Mar 2010 12:33:34 +0100
branchSymbian3
changeset 4 837f303aceeb
permissions -rw-r--r--
Current Symbian^3 public API header files (from PDK 3.0.h)
This is the epoc32/include tree with the "platform" subtrees removed, and
all but a selected few mbg and rsg files removed.
     1 //=======================================================================
     2 // Copyright 2000 University of Notre Dame.
     3 // Authors: Jeremy G. Siek, Andrew Lumsdaine, Lie-Quan Lee
     4 //
     5 // Distributed under the Boost Software License, Version 1.0. (See
     6 // accompanying file LICENSE_1_0.txt or copy at
     7 // http://www.boost.org/LICENSE_1_0.txt)
     8 //=======================================================================
     9 
    10 #ifndef BOOST_EDGE_CONNECTIVITY
    11 #define BOOST_EDGE_CONNECTIVITY
    12 
    13 // WARNING: not-yet fully tested!
    14 
    15 #include <boost/config.hpp>
    16 #include <vector>
    17 #include <set>
    18 #include <algorithm>
    19 #include <boost/graph/edmunds_karp_max_flow.hpp>
    20 
    21 namespace boost {
    22 
    23   namespace detail {
    24 
    25     template <class Graph>
    26     inline
    27     std::pair<typename graph_traits<Graph>::vertex_descriptor,
    28               typename graph_traits<Graph>::degree_size_type>
    29     min_degree_vertex(Graph& g)
    30     {
    31       typedef graph_traits<Graph> Traits;
    32       typename Traits::vertex_descriptor p;
    33       typedef typename Traits::degree_size_type size_type;
    34       size_type delta = (std::numeric_limits<size_type>::max)();
    35 
    36       typename Traits::vertex_iterator i, iend;
    37       for (tie(i, iend) = vertices(g); i != iend; ++i)
    38         if (degree(*i, g) < delta) {
    39           delta = degree(*i, g);
    40           p = *i;
    41         }
    42       return std::make_pair(p, delta);
    43     }
    44 
    45     template <class Graph, class OutputIterator>
    46     void neighbors(const Graph& g, 
    47                    typename graph_traits<Graph>::vertex_descriptor u,
    48                    OutputIterator result)
    49     {
    50       typename graph_traits<Graph>::adjacency_iterator ai, aend;
    51       for (tie(ai, aend) = adjacent_vertices(u, g); ai != aend; ++ai)
    52         *result++ = *ai;
    53     }
    54 
    55     template <class Graph, class VertexIterator, class OutputIterator>
    56     void neighbors(const Graph& g, 
    57                    VertexIterator first, VertexIterator last,
    58                    OutputIterator result)
    59     {
    60       for (; first != last; ++first)
    61         neighbors(g, *first, result);
    62     }
    63 
    64   } // namespace detail
    65 
    66   // O(m n)
    67   template <class VertexListGraph, class OutputIterator>
    68   typename graph_traits<VertexListGraph>::degree_size_type
    69   edge_connectivity(VertexListGraph& g, OutputIterator disconnecting_set)
    70   {
    71     //-------------------------------------------------------------------------
    72     // Type Definitions
    73     typedef graph_traits<VertexListGraph> Traits;
    74     typedef typename Traits::vertex_iterator vertex_iterator;
    75     typedef typename Traits::edge_iterator edge_iterator;
    76     typedef typename Traits::out_edge_iterator out_edge_iterator;
    77     typedef typename Traits::vertex_descriptor vertex_descriptor;
    78     typedef typename Traits::degree_size_type degree_size_type;
    79     typedef color_traits<default_color_type> Color;
    80 
    81     typedef adjacency_list_traits<vecS, vecS, directedS> Tr;
    82     typedef typename Tr::edge_descriptor Tr_edge_desc;
    83     typedef adjacency_list<vecS, vecS, directedS, no_property, 
    84       property<edge_capacity_t, degree_size_type,
    85         property<edge_residual_capacity_t, degree_size_type,
    86           property<edge_reverse_t, Tr_edge_desc> > > > 
    87       FlowGraph;
    88     typedef typename graph_traits<FlowGraph>::edge_descriptor edge_descriptor;
    89 
    90     //-------------------------------------------------------------------------
    91     // Variable Declarations
    92     vertex_descriptor u, v, p, k;
    93     edge_descriptor e1, e2;
    94     bool inserted;
    95     vertex_iterator vi, vi_end;
    96     edge_iterator ei, ei_end;
    97     degree_size_type delta, alpha_star, alpha_S_k;
    98     std::set<vertex_descriptor> S, neighbor_S;
    99     std::vector<vertex_descriptor> S_star, non_neighbor_S;
   100     std::vector<default_color_type> color(num_vertices(g));
   101     std::vector<edge_descriptor> pred(num_vertices(g));
   102 
   103     //-------------------------------------------------------------------------
   104     // Create a network flow graph out of the undirected graph
   105     FlowGraph flow_g(num_vertices(g));
   106 
   107     typename property_map<FlowGraph, edge_capacity_t>::type
   108       cap = get(edge_capacity, flow_g);
   109     typename property_map<FlowGraph, edge_residual_capacity_t>::type
   110       res_cap = get(edge_residual_capacity, flow_g);
   111     typename property_map<FlowGraph, edge_reverse_t>::type
   112       rev_edge = get(edge_reverse, flow_g);
   113 
   114     for (tie(ei, ei_end) = edges(g); ei != ei_end; ++ei) {
   115       u = source(*ei, g), v = target(*ei, g);
   116       tie(e1, inserted) = add_edge(u, v, flow_g);
   117       cap[e1] = 1;
   118       tie(e2, inserted) = add_edge(v, u, flow_g);
   119       cap[e2] = 1; // not sure about this
   120       rev_edge[e1] = e2;
   121       rev_edge[e2] = e1;
   122     }
   123 
   124     //-------------------------------------------------------------------------
   125     // The Algorithm
   126 
   127     tie(p, delta) = detail::min_degree_vertex(g);
   128     S_star.push_back(p);
   129     alpha_star = delta;
   130     S.insert(p);
   131     neighbor_S.insert(p);
   132     detail::neighbors(g, S.begin(), S.end(), 
   133                       std::inserter(neighbor_S, neighbor_S.begin()));
   134 
   135     std::set_difference(vertices(g).first, vertices(g).second,
   136                         neighbor_S.begin(), neighbor_S.end(),
   137                         std::back_inserter(non_neighbor_S));
   138 
   139     while (!non_neighbor_S.empty()) { // at most n - 1 times
   140       k = non_neighbor_S.front();
   141 
   142       alpha_S_k = edmunds_karp_max_flow
   143         (flow_g, p, k, cap, res_cap, rev_edge, &color[0], &pred[0]);
   144 
   145       if (alpha_S_k < alpha_star) {
   146         alpha_star = alpha_S_k;
   147         S_star.clear();
   148         for (tie(vi, vi_end) = vertices(flow_g); vi != vi_end; ++vi)
   149           if (color[*vi] != Color::white())
   150             S_star.push_back(*vi);
   151       }
   152       S.insert(k);
   153       neighbor_S.insert(k);
   154       detail::neighbors(g, k, std::inserter(neighbor_S, neighbor_S.begin()));
   155       non_neighbor_S.clear();
   156       std::set_difference(vertices(g).first, vertices(g).second,
   157                           neighbor_S.begin(), neighbor_S.end(),
   158                           std::back_inserter(non_neighbor_S));
   159     }
   160     //-------------------------------------------------------------------------
   161     // Compute edges of the cut [S*, ~S*]
   162     std::vector<bool> in_S_star(num_vertices(g), false);
   163     typename std::vector<vertex_descriptor>::iterator si;
   164     for (si = S_star.begin(); si != S_star.end(); ++si)
   165       in_S_star[*si] = true;
   166 
   167     degree_size_type c = 0;
   168     for (si = S_star.begin(); si != S_star.end(); ++si) {
   169       out_edge_iterator ei, ei_end;
   170       for (tie(ei, ei_end) = out_edges(*si, g); ei != ei_end; ++ei)
   171         if (!in_S_star[target(*ei, g)]) {
   172           *disconnecting_set++ = *ei;
   173           ++c;
   174         }
   175     }
   176     return c;
   177   }
   178 
   179 } // namespace boost
   180 
   181 #endif // BOOST_EDGE_CONNECTIVITY