# HG changeset patch
# User kpeter
# Date 1204167456 0
# Node ID 7216b6a52ab902375682bb942fd507094f775464
# Parent  4f1ac622bb7aa01ba135960cc657f45edd7d3ec1
Small fixes and doc improvements in MinMeanCycle.

diff -r 4f1ac622bb7a -r 7216b6a52ab9 lemon/min_mean_cycle.h
--- a/lemon/min_mean_cycle.h	Thu Feb 28 02:55:23 2008 +0000
+++ b/lemon/min_mean_cycle.h	Thu Feb 28 02:57:36 2008 +0000
@@ -26,9 +26,9 @@
 
 #include <vector>
 #include <lemon/graph_utils.h>
-#include <lemon/topology.h>
 #include <lemon/path.h>
 #include <lemon/tolerance.h>
+#include <lemon/topology.h>
 
 namespace lemon {
 
@@ -41,8 +41,8 @@
   /// \ref MinMeanCycle implements Howard's algorithm for finding a
   /// minimum mean directed cycle.
   ///
-  /// \param Graph The directed graph type the algorithm runs on.
-  /// \param LengthMap The type of the length (cost) map.
+  /// \tparam Graph The directed graph type the algorithm runs on.
+  /// \tparam LengthMap The type of the length (cost) map.
   ///
   /// \warning \c LengthMap::Value must be convertible to \c double.
   ///
@@ -57,28 +57,28 @@
     typedef typename LengthMap::Value Length;
     typedef Path<Graph> Path;
 
-  protected:
+  private:
 
-    typename Graph::template NodeMap<bool> _reached;
-    typename Graph::template NodeMap<double> _dist;
-    typename Graph::template NodeMap<Edge> _policy;
-
-    /// The directed graph the algorithm runs on.
+    // The directed graph the algorithm runs on
     const Graph &_graph;
-    /// The length of the edges.
+    // The length of the edges
     const LengthMap &_length;
 
-    /// The total length of the found cycle.
+    // The total length of the found cycle
     Length _cycle_length;
-    /// The number of edges on the found cycle.
+    // The number of edges on the found cycle
     int _cycle_size;
-    /// The found cycle.
+    // The found cycle
     Path *_cycle_path;
 
     bool _local_path;
     bool _cycle_found;
     Node _cycle_node;
 
+    typename Graph::template NodeMap<bool> _reached;
+    typename Graph::template NodeMap<double> _dist;
+    typename Graph::template NodeMap<Edge> _policy;
+
     typename Graph::template NodeMap<int> _component;
     int _component_num;
 
@@ -96,171 +96,55 @@
     /// \param length The length (cost) of the edges.
     MinMeanCycle( const Graph &graph,
                   const LengthMap &length ) :
-      _graph(graph), _length(length), _dist(graph), _reached(graph),
-      _policy(graph), _component(graph), _cycle_length(0),
-      _cycle_size(-1), _cycle_path(NULL), _local_path(false)
-    { }
+      _graph(graph), _length(length), _cycle_length(0), _cycle_size(-1),
+      _cycle_path(NULL), _local_path(false), _reached(graph),
+      _dist(graph), _policy(graph), _component(graph)
+    {}
 
     /// The destructor of the class.
     ~MinMeanCycle() {
       if (_local_path) delete _cycle_path;
     }
 
-  protected:
-
-    // Initializes the internal data structures for the current strongly
-    // connected component and creating the policy graph.
-    // The policy graph can be represented by the _policy map because
-    // the out degree of every node is 1.
-    bool initCurrentComponent(int comp) {
-      // Finding the nodes of the current component
-      _nodes.clear();
-      for (NodeIt n(_graph); n != INVALID; ++n) {
-        if (_component[n] == comp) _nodes.push_back(n);
+    /// \brief Sets the \ref Path "path" structure for storing the found
+    /// cycle.
+    ///
+    /// Sets an external \ref Path "path" structure for storing the
+    /// found cycle.
+    ///
+    /// If you don't call this function before calling \ref run() or
+    /// \ref init(), it will allocate a local \ref Path "path"
+    /// structure.
+    /// The destuctor deallocates this automatically allocated map,
+    /// of course.
+    ///
+    /// \note The algorithm calls only the \ref lemon::Path::addBack()
+    /// "addBack()" function of the given \ref Path "path" structure.
+    ///
+    /// \return <tt>(*this)</tt>
+    ///
+    /// \sa cycle()
+    MinMeanCycle& cyclePath(Path &path) {
+      if (_local_path) {
+        delete _cycle_path;
+        _local_path = false;
       }
-      if (_nodes.size() <= 1) return false;
-      // Finding the edges of the current component
-      _edges.clear();
-      for (EdgeIt e(_graph); e != INVALID; ++e) {
-        if ( _component[_graph.source(e)] == comp &&
-             _component[_graph.target(e)] == comp )
-          _edges.push_back(e);
-      }
-      // Initializing _reached, _dist, _policy maps
-      for (int i = 0; i < _nodes.size(); ++i) {
-        _reached[_nodes[i]] = false;
-        _policy[_nodes[i]] = INVALID;
-      }
-      Node u; Edge e;
-      for (int j = 0; j < _edges.size(); ++j) {
-        e = _edges[j];
-        u = _graph.source(e);
-        if (!_reached[u] || _length[e] < _dist[u]) {
-          _dist[u] = _length[e];
-          _policy[u] = e;
-          _reached[u] = true;
-        }
-      }
-      return true;
+      _cycle_path = &path;
+      return *this;
     }
 
-    // Finds all cycles in the policy graph.
-    // Sets _cycle_found to true if a cycle is found and sets
-    // _cycle_length, _cycle_size, _cycle_node to represent the minimum
-    // mean cycle in the policy graph.
-    bool findPolicyCycles(int comp) {
-      typename Graph::template NodeMap<int> level(_graph, -1);
-      _cycle_found = false;
-      Length clength;
-      int csize;
-      int path_cnt = 0;
-      Node u, v;
-      // Searching for cycles
-      for (int i = 0; i < _nodes.size(); ++i) {
-        if (level[_nodes[i]] < 0) {
-          u = _nodes[i];
-          level[u] = path_cnt;
-          while (level[u = _graph.target(_policy[u])] < 0)
-            level[u] = path_cnt;
-          if (level[u] == path_cnt) {
-            // A cycle is found
-            clength = _length[_policy[u]];
-            csize = 1;
-            for (v = u; (v = _graph.target(_policy[v])) != u; ) {
-              clength += _length[_policy[v]];
-              ++csize;
-            }
-            if ( !_cycle_found ||
-                 clength * _cycle_size < _cycle_length * csize ) {
-              _cycle_found = true;
-              _cycle_length = clength;
-              _cycle_size = csize;
-              _cycle_node = u;
-            }
-          }
-          ++path_cnt;
-        }
-      }
-      return _cycle_found;
-    }
+    /// \name Execution control
+    /// The simplest way to execute the algorithm is to call run().
+    /// \n
+    /// If you only need the minimum mean value, you may call init()
+    /// and findMinMean().
+    /// \n
+    /// If you would like to run the algorithm again (e.g. the
+    /// underlaying graph and/or the edge costs were modified), you may
+    /// not create a new instance of the class, rather call reset(),
+    /// findMinMean(), and findCycle() instead.
 
-    // Contracts the policy graph to be connected by cutting all cycles
-    // except for the main cycle (i.e. the minimum mean cycle).
-    void contractPolicyGraph(int comp) {
-      // Finding the component of the main cycle using
-      // reverse BFS search
-      typename Graph::template NodeMap<int> found(_graph, false);
-      std::deque<Node> queue;
-      queue.push_back(_cycle_node);
-      found[_cycle_node] = true;
-      Node u, v;
-      while (!queue.empty()) {
-        v = queue.front(); queue.pop_front();
-        for (InEdgeIt e(_graph, v); e != INVALID; ++e) {
-          u = _graph.source(e);
-          if (_component[u] == comp && !found[u] && _policy[u] == e) {
-            found[u] = true;
-            queue.push_back(u);
-          }
-        }
-      }
-      // Connecting all other nodes to this component using
-      // reverse BFS search
-      queue.clear();
-      for (int i = 0; i < _nodes.size(); ++i)
-        if (found[_nodes[i]]) queue.push_back(_nodes[i]);
-      int found_cnt = queue.size();
-      while (found_cnt < _nodes.size() && !queue.empty()) {
-        v = queue.front(); queue.pop_front();
-        for (InEdgeIt e(_graph, v); e != INVALID; ++e) {
-          u = _graph.source(e);
-          if (_component[u] == comp && !found[u]) {
-            found[u] = true;
-            ++found_cnt;
-            _policy[u] = e;
-            queue.push_back(u);
-          }
-        }
-      }
-    }
-
-    // Computes node distances in the policy graph and updates the
-    // policy graph if the node distances can be improved.
-    bool computeNodeDistances(int comp) {
-      // Computing node distances using reverse BFS search
-      double cycle_mean = (double)_cycle_length / _cycle_size;
-      typename Graph::template NodeMap<int> found(_graph, false);
-      std::deque<Node> queue;
-      queue.push_back(_cycle_node);
-      found[_cycle_node] = true;
-      Node u, v;
-      while (!queue.empty()) {
-        v = queue.front(); queue.pop_front();
-        for (InEdgeIt e(_graph, v); e != INVALID; ++e) {
-          u = _graph.source(e);
-          if (_component[u] == comp && !found[u] && _policy[u] == e) {
-            found[u] = true;
-            _dist[u] = _dist[v] + _length[e] - cycle_mean;
-            queue.push_back(u);
-          }
-        }
-      }
-      // Improving node distances
-      bool improved = false;
-      for (int j = 0; j < _edges.size(); ++j) {
-        Edge e = _edges[j];
-        u = _graph.source(e); v = _graph.target(e);
-        double delta = _dist[v] + _length[e] - cycle_mean;
-        if (_tolerance.less(delta, _dist[u])) {
-          improved = true;
-          _dist[u] = delta;
-          _policy[u] = e;
-        }
-      }
-      return improved;
-    }
-
-  public:
+    /// @{
 
     /// \brief Runs the algorithm.
     ///
@@ -286,7 +170,7 @@
     ///
     /// \sa reset()
     void init() {
-      _tolerance.epsilon(1e-8);
+      _tolerance.epsilon(1e-6);
       if (!_cycle_path) {
         _local_path = true;
         _cycle_path = new Path;
@@ -321,11 +205,12 @@
       for (int comp = 0; comp < _component_num; ++comp) {
         if (!initCurrentComponent(comp)) continue;
         while (true) {
-          if (!findPolicyCycles(comp)) return false;
+          if (!findPolicyCycles()) break;
           contractPolicyGraph(comp);
-          if (!computeNodeDistances(comp)) return true;
+          if (!computeNodeDistances(comp)) break;
         }
       }
+      return _cycle_found;
     }
 
     /// \brief Finds a critical (minimum mean) directed cycle.
@@ -346,7 +231,16 @@
       }
       return true;
     }
+    
+    /// @}
 
+    /// \name Query Functions
+    /// The result of the algorithm can be obtained using these
+    /// functions.
+    /// \n run() must be called before using them.
+
+    /// @{
+    
     /// \brief Returns the total length of the found cycle.
     ///
     /// Returns the total length of the found cycle.
@@ -380,7 +274,7 @@
     ///   return double(mmc.cycleLength()) / mmc.cycleEdgeNum();
     /// \endcode
     double cycleMean() const {
-      return (double)_cycle_length / _cycle_size;
+      return double(_cycle_length) / _cycle_size;
     }
 
     /// \brief Returns a const reference to the \ref Path "path"
@@ -396,32 +290,163 @@
     const Path& cycle() const {
       return *_cycle_path;
     }
+    
+    ///@}
+    
+  private:
 
-    /// \brief Sets the \ref Path "path" structure for storing the found
-    /// cycle.
-    ///
-    /// Sets an external \ref Path "path" structure for storing the
-    /// found cycle.
-    ///
-    /// If you don't call this function before calling \ref run() or
-    /// \ref init(), it will allocate a local \ref Path "path"
-    /// structure.
-    /// The destuctor deallocates this automatically allocated map,
-    /// of course.
-    ///
-    /// \note The algorithm calls only the \ref lemon::Path::addBack()
-    /// "addBack()" function of the given \ref Path "path" structure.
-    ///
-    /// \return <tt>(*this)</tt>
-    ///
-    /// \sa cycle()
-    MinMeanCycle& cyclePath(Path &path) {
-      if (_local_path) {
-        delete _cycle_path;
-        _local_path = false;
+    // Initializes the internal data structures for the current strongly
+    // connected component and creating the policy graph.
+    // The policy graph can be represented by the _policy map because
+    // the out degree of every node is 1.
+    bool initCurrentComponent(int comp) {
+      // Finding the nodes of the current component
+      _nodes.clear();
+      for (NodeIt n(_graph); n != INVALID; ++n) {
+        if (_component[n] == comp) _nodes.push_back(n);
       }
-      _cycle_path = &path;
-      return *this;
+      if (_nodes.size() <= 1) return false;
+      // Finding the edges of the current component
+      _edges.clear();
+      for (EdgeIt e(_graph); e != INVALID; ++e) {
+        if ( _component[_graph.source(e)] == comp &&
+             _component[_graph.target(e)] == comp )
+          _edges.push_back(e);
+      }
+      // Initializing _reached, _dist, _policy maps
+      for (int i = 0; i < int(_nodes.size()); ++i) {
+        _reached[_nodes[i]] = false;
+        _policy[_nodes[i]] = INVALID;
+      }
+      Node u; Edge e;
+      for (int j = 0; j < int(_edges.size()); ++j) {
+        e = _edges[j];
+        u = _graph.source(e);
+        if (!_reached[u] || _length[e] < _dist[u]) {
+          _dist[u] = _length[e];
+          _policy[u] = e;
+          _reached[u] = true;
+        }
+      }
+      return true;
+    }
+
+    // Finds all cycles in the policy graph.
+    // Sets _cycle_found to true if a cycle is found and sets
+    // _cycle_length, _cycle_size, _cycle_node to represent the minimum
+    // mean cycle in the policy graph.
+    bool findPolicyCycles() {
+      typename Graph::template NodeMap<int> level(_graph, -1);
+      bool curr_cycle_found = false;
+      Length clength;
+      int csize;
+      int path_cnt = 0;
+      Node u, v;
+      // Searching for cycles
+      for (int i = 0; i < int(_nodes.size()); ++i) {
+        if (level[_nodes[i]] < 0) {
+          u = _nodes[i];
+          level[u] = path_cnt;
+          while (level[u = _graph.target(_policy[u])] < 0)
+            level[u] = path_cnt;
+          if (level[u] == path_cnt) {
+            // A cycle is found
+            curr_cycle_found = true;
+            clength = _length[_policy[u]];
+            csize = 1;
+            for (v = u; (v = _graph.target(_policy[v])) != u; ) {
+              clength += _length[_policy[v]];
+              ++csize;
+            }
+            if ( !_cycle_found ||
+                 clength * _cycle_size < _cycle_length * csize ) {
+              _cycle_found = true;
+              _cycle_length = clength;
+              _cycle_size = csize;
+              _cycle_node = u;
+            }
+          }
+          ++path_cnt;
+        }
+      }
+      return curr_cycle_found;
+    }
+
+    // Contracts the policy graph to be connected by cutting all cycles
+    // except for the main cycle (i.e. the minimum mean cycle).
+    void contractPolicyGraph(int comp) {
+      // Finding the component of the main cycle using
+      // reverse BFS search
+      typename Graph::template NodeMap<int> found(_graph, false);
+      std::deque<Node> queue;
+      queue.push_back(_cycle_node);
+      found[_cycle_node] = true;
+      Node u, v;
+      while (!queue.empty()) {
+        v = queue.front(); queue.pop_front();
+        for (InEdgeIt e(_graph, v); e != INVALID; ++e) {
+          u = _graph.source(e);
+          if (_component[u] == comp && !found[u] && _policy[u] == e) {
+            found[u] = true;
+            queue.push_back(u);
+          }
+        }
+      }
+      // Connecting all other nodes to this component using
+      // reverse BFS search
+      queue.clear();
+      for (int i = 0; i < int(_nodes.size()); ++i)
+        if (found[_nodes[i]]) queue.push_back(_nodes[i]);
+      int found_cnt = queue.size();
+      while (found_cnt < int(_nodes.size()) && !queue.empty()) {
+        v = queue.front(); queue.pop_front();
+        for (InEdgeIt e(_graph, v); e != INVALID; ++e) {
+          u = _graph.source(e);
+          if (_component[u] == comp && !found[u]) {
+            found[u] = true;
+            ++found_cnt;
+            _policy[u] = e;
+            queue.push_back(u);
+          }
+        }
+      }
+    }
+
+    // Computes node distances in the policy graph and updates the
+    // policy graph if the node distances can be improved.
+    bool computeNodeDistances(int comp) {
+      // Computing node distances using reverse BFS search
+      double cycle_mean = double(_cycle_length) / _cycle_size;
+      typename Graph::template NodeMap<int> found(_graph, false);
+      std::deque<Node> queue;
+      queue.push_back(_cycle_node);
+      found[_cycle_node] = true;
+      _dist[_cycle_node] = 0;
+      Node u, v;
+      while (!queue.empty()) {
+        v = queue.front(); queue.pop_front();
+        for (InEdgeIt e(_graph, v); e != INVALID; ++e) {
+          u = _graph.source(e);
+          if (_component[u] == comp && !found[u] && _policy[u] == e) {
+            found[u] = true;
+            _dist[u] = _dist[v] + _length[e] - cycle_mean;
+            queue.push_back(u);
+          }
+        }
+      }
+      // Improving node distances
+      bool improved = false;
+      for (int j = 0; j < int(_edges.size()); ++j) {
+        Edge e = _edges[j];
+        u = _graph.source(e); v = _graph.target(e);
+        double delta = _dist[v] + _length[e] - cycle_mean;
+        if (_tolerance.less(delta, _dist[u])) {
+          improved = true;
+          _dist[u] = delta;
+          _policy[u] = e;
+        }
+      }
+      return improved;
     }
 
   }; //class MinMeanCycle