Changes in / [998:3ffd46dc8e01:997:a725503acfe9] in lemon

File:

• lemon/network_simplex.h (modified) (26 diffs)

lemon/network_simplex.h

@@ -167 +167 @@
     typedef std::vector<Value> ValueVector;
     typedef std::vector<Cost> CostVector;
-    typedef std::vector<signed char> CharVector;
-    // Note: vector<signed char> is used instead of vector<ArcState> and 
-    // vector<ArcDirection> for efficiency reasons
+    typedef std::vector<char> BoolVector;
+    // Note: vector<char> is used instead of vector<bool> for efficiency reasons
 
     // State constants for arcs
@@ -178 +177 @@
     };
 
-    // Direction constants for tree arcs
-    enum ArcDirection {
-      DIR_DOWN = -1,
-      DIR_UP   =  1
-    };
+    typedef std::vector<signed char> StateVector;
+    // Note: vector<signed char> is used instead of vector<ArcState> for
+    // efficiency reasons
 
   private:
@@ -221 +218 @@
     IntVector _succ_num;
     IntVector _last_succ;
-    CharVector _pred_dir;
-    CharVector _state;
     IntVector _dirty_revs;
+    BoolVector _forward;
+    StateVector _state;
     int _root;
 
     // Temporary data used in the current pivot iteration
     int in_arc, join, u_in, v_in, u_out, v_out;
+    int first, second, right, last;
+    int stem, par_stem, new_stem;
     Value delta;
 
@@ -252 +251 @@
       const IntVector  &_target;
       const CostVector &_cost;
-      const CharVector &_state;
+      const StateVector &_state;
       const CostVector &_pi;
       int &_in_arc;
@@ -304 +303 @@
       const IntVector  &_target;
       const CostVector &_cost;
-      const CharVector &_state;
+      const StateVector &_state;
       const CostVector &_pi;
       int &_in_arc;
@@ -343 +342 @@
       const IntVector  &_target;
       const CostVector &_cost;
-      const CharVector &_state;
+      const StateVector &_state;
       const CostVector &_pi;
       int &_in_arc;
@@ -416 +415 @@
       const IntVector  &_target;
       const CostVector &_cost;
-      const CharVector &_state;
+      const StateVector &_state;
       const CostVector &_pi;
       int &_in_arc;
@@ -519 +518 @@
       const IntVector  &_target;
       const CostVector &_cost;
-      const CharVector &_state;
+      const StateVector &_state;
       const CostVector &_pi;
       int &_in_arc;
@@ -572 +571 @@
         // Check the current candidate list
         int e;
-        Cost c;
         for (int i = 0; i != _curr_length; ++i) {
           e = _candidates[i];
-          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
-          if (c < 0) {
-            _cand_cost[e] = c;
-          } else {
+          _cand_cost[e] = _state[e] *
+            (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
+          if (_cand_cost[e] >= 0) {
             _candidates[i--] = _candidates[--_curr_length];
           }
@@ -588 +585 @@
 
         for (e = _next_arc; e != _search_arc_num; ++e) {
-          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
-          if (c < 0) {
-            _cand_cost[e] = c;
+          _cand_cost[e] = _state[e] *
+            (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
+          if (_cand_cost[e] < 0) {
             _candidates[_curr_length++] = e;
           }
@@ -637 +634 @@
     ///
     /// \param graph The digraph the algorithm runs on.
-    /// \param arc_mixing Indicate if the arcs will be stored in a
+    /// \param arc_mixing Indicate if the arcs have to be stored in a
     /// mixed order in the internal data structure.
-    /// In general, it leads to similar performance as using the original
-    /// arc order, but it makes the algorithm more robust and in special
-    /// cases, even significantly faster. Therefore, it is enabled by default.
-    NetworkSimplex(const GR& graph, bool arc_mixing = true) :
+    /// In special cases, it could lead to better overall performance,
+    /// but it is usually slower. Therefore it is disabled by default.
+    NetworkSimplex(const GR& graph, bool arc_mixing = false) :
       _graph(graph), _node_id(graph), _arc_id(graph),
       _arc_mixing(arc_mixing),
@@ -918 +914 @@
       _parent.resize(all_node_num);
       _pred.resize(all_node_num);
-      _pred_dir.resize(all_node_num);
+      _forward.resize(all_node_num);
       _thread.resize(all_node_num);
       _rev_thread.resize(all_node_num);
@@ -932 +928 @@
       if (_arc_mixing) {
         // Store the arcs in a mixed order
-        const int skip = std::max(_arc_num / _node_num, 3);
+        int k = std::max(int(std::sqrt(double(_arc_num))), 10);
         int i = 0, j = 0;
         for (ArcIt a(_graph); a != INVALID; ++a) {
@@ -938 +934 @@
           _source[i] = _node_id[_graph.source(a)];
           _target[i] = _node_id[_graph.target(a)];
-          if ((i += skip) >= _arc_num) i = ++j;
+          if ((i += k) >= _arc_num) i = ++j;
         }
       } else {
@@ -1121 +1117 @@
           _state[e] = STATE_TREE;
           if (_supply[u] >= 0) {
-            _pred_dir[u] = DIR_UP;
+            _forward[u] = true;
             _pi[u] = 0;
             _source[e] = u;
@@ -1128 +1124 @@
             _cost[e] = 0;
           } else {
-            _pred_dir[u] = DIR_DOWN;
+            _forward[u] = false;
             _pi[u] = ART_COST;
             _source[e] = _root;
@@ -1148 +1144 @@
           _last_succ[u] = u;
           if (_supply[u] >= 0) {
-            _pred_dir[u] = DIR_UP;
+            _forward[u] = true;
             _pi[u] = 0;
             _pred[u] = e;
@@ -1158 +1154 @@
             _state[e] = STATE_TREE;
           } else {
-            _pred_dir[u] = DIR_DOWN;
+            _forward[u] = false;
             _pi[u] = ART_COST;
             _pred[u] = f;
@@ -1189 +1185 @@
           _last_succ[u] = u;
           if (_supply[u] <= 0) {
-            _pred_dir[u] = DIR_DOWN;
+            _forward[u] = false;
             _pi[u] = 0;
             _pred[u] = e;
@@ -1199 +1195 @@
             _state[e] = STATE_TREE;
           } else {
-            _pred_dir[u] = DIR_UP;
+            _forward[u] = true;
             _pi[u] = -ART_COST;
             _pred[u] = f;
@@ -1242 +1238 @@
       // Initialize first and second nodes according to the direction
       // of the cycle
-      int first, second;
       if (_state[in_arc] == STATE_LOWER) {
         first  = _source[in_arc];
@@ -1252 +1247 @@
       delta = _cap[in_arc];
       int result = 0;
-      Value c, d;
+      Value d;
       int e;
 
-      // Search the cycle form the first node to the join node
+      // Search the cycle along the path form the first node to the root
       for (int u = first; u != join; u = _parent[u]) {
         e = _pred[u];
-        d = _flow[e];
-        if (_pred_dir[u] == DIR_DOWN) {
-          c = _cap[e];
-          d = c >= MAX ? INF : c - d;
-        }
+        d = _forward[u] ?
+          _flow[e] : (_cap[e] >= MAX ? INF : _cap[e] - _flow[e]);
         if (d < delta) {
           delta = d;
@@ -1269 +1261 @@
         }
       }
-
-      // Search the cycle form the second node to the join node
+      // Search the cycle along the path form the second node to the root
       for (int u = second; u != join; u = _parent[u]) {
         e = _pred[u];
-        d = _flow[e];
-        if (_pred_dir[u] == DIR_UP) {
-          c = _cap[e];
-          d = c >= MAX ? INF : c - d;
-        }
+        d = _forward[u] ?
+          (_cap[e] >= MAX ? INF : _cap[e] - _flow[e]) : _flow[e];
         if (d <= delta) {
           delta = d;
@@ -1302 +1290 @@
         _flow[in_arc] += val;
         for (int u = _source[in_arc]; u != join; u = _parent[u]) {
-          _flow[_pred[u]] -= _pred_dir[u] * val;
+          _flow[_pred[u]] += _forward[u] ? -val : val;
         }
         for (int u = _target[in_arc]; u != join; u = _parent[u]) {
-          _flow[_pred[u]] += _pred_dir[u] * val;
+          _flow[_pred[u]] += _forward[u] ? val : -val;
         }
       }
@@ -1320 +1308 @@
     // Update the tree structure
     void updateTreeStructure() {
+      int u, w;
       int old_rev_thread = _rev_thread[u_out];
       int old_succ_num = _succ_num[u_out];
@@ -1325 +1314 @@
       v_out = _parent[u_out];
 
-      // Check if u_in and u_out coincide
-      if (u_in == u_out) {
-        // Update _parent, _pred, _pred_dir
-        _parent[u_in] = v_in;
-        _pred[u_in] = in_arc;
-        _pred_dir[u_in] = u_in == _source[in_arc] ? DIR_UP : DIR_DOWN;
-
-        // Update _thread and _rev_thread
-        if (_thread[v_in] != u_out) {
-          int after = _thread[old_last_succ];
-          _thread[old_rev_thread] = after;
-          _rev_thread[after] = old_rev_thread;
-          after = _thread[v_in];
-          _thread[v_in] = u_out;
-          _rev_thread[u_out] = v_in;
-          _thread[old_last_succ] = after;
-          _rev_thread[after] = old_last_succ;
-        }
+      u = _last_succ[u_in];  // the last successor of u_in
+      right = _thread[u];    // the node after it
+
+      // Handle the case when old_rev_thread equals to v_in
+      // (it also means that join and v_out coincide)
+      if (old_rev_thread == v_in) {
+        last = _thread[_last_succ[u_out]];
       } else {
-        // Handle the case when old_rev_thread equals to v_in
-        // (it also means that join and v_out coincide)
-        int thread_continue = old_rev_thread == v_in ?
-          _thread[old_last_succ] : _thread[v_in];
-
-        // Update _thread and _parent along the stem nodes (i.e. the nodes
-        // between u_in and u_out, whose parent have to be changed)
-        int stem = u_in;              // the current stem node
-        int par_stem = v_in;          // the new parent of stem
-        int next_stem;                // the next stem node
-        int last = _last_succ[u_in];  // the last successor of stem
-        int before, after = _thread[last];
-        _thread[v_in] = u_in;
-        _dirty_revs.clear();
-        _dirty_revs.push_back(v_in);
-        while (stem != u_out) {
-          // Insert the next stem node into the thread list
-          next_stem = _parent[stem];
-          _thread[last] = next_stem;
-          _dirty_revs.push_back(last);
-
-          // Remove the subtree of stem from the thread list
-          before = _rev_thread[stem];
-          _thread[before] = after;
-          _rev_thread[after] = before;
-
-          // Change the parent node and shift stem nodes
-          _parent[stem] = par_stem;
-          par_stem = stem;
-          stem = next_stem;
-
-          // Update last and after
-          last = _last_succ[stem] == _last_succ[par_stem] ?
-            _rev_thread[par_stem] : _last_succ[stem];
-          after = _thread[last];
-        }
-        _parent[u_out] = par_stem;
-        _thread[last] = thread_continue;
-        _rev_thread[thread_continue] = last;
-        _last_succ[u_out] = last;
-
-        // Remove the subtree of u_out from the thread list except for
-        // the case when old_rev_thread equals to v_in
-        if (old_rev_thread != v_in) {
-          _thread[old_rev_thread] = after;
-          _rev_thread[after] = old_rev_thread;
-        }
-
-        // Update _rev_thread using the new _thread values
-        for (int i = 0; i != int(_dirty_revs.size()); ++i) {
-          int u = _dirty_revs[i];
-          _rev_thread[_thread[u]] = u;
-        }
-
-        // Update _pred, _pred_dir, _last_succ and _succ_num for the
-        // stem nodes from u_out to u_in
-        int tmp_sc = 0, tmp_ls = _last_succ[u_out];
-        for (int u = u_out, p = _parent[u]; u != u_in; u = p, p = _parent[u]) {
-          _pred[u] = _pred[p];
-          _pred_dir[u] = -_pred_dir[p];
-          tmp_sc += _succ_num[u] - _succ_num[p];
-          _succ_num[u] = tmp_sc;
-          _last_succ[p] = tmp_ls;
-        }
-        _pred[u_in] = in_arc;
-        _pred_dir[u_in] = u_in == _source[in_arc] ? DIR_UP : DIR_DOWN;
-        _succ_num[u_in] = old_succ_num;
+        last = _thread[v_in];
+      }
+
+      // Update _thread and _parent along the stem nodes (i.e. the nodes
+      // between u_in and u_out, whose parent have to be changed)
+      _thread[v_in] = stem = u_in;
+      _dirty_revs.clear();
+      _dirty_revs.push_back(v_in);
+      par_stem = v_in;
+      while (stem != u_out) {
+        // Insert the next stem node into the thread list
+        new_stem = _parent[stem];
+        _thread[u] = new_stem;
+        _dirty_revs.push_back(u);
+
+        // Remove the subtree of stem from the thread list
+        w = _rev_thread[stem];
+        _thread[w] = right;
+        _rev_thread[right] = w;
+
+        // Change the parent node and shift stem nodes
+        _parent[stem] = par_stem;
+        par_stem = stem;
+        stem = new_stem;
+
+        // Update u and right
+        u = _last_succ[stem] == _last_succ[par_stem] ?
+          _rev_thread[par_stem] : _last_succ[stem];
+        right = _thread[u];
+      }
+      _parent[u_out] = par_stem;
+      _thread[u] = last;
+      _rev_thread[last] = u;
+      _last_succ[u_out] = u;
+
+      // Remove the subtree of u_out from the thread list except for
+      // the case when old_rev_thread equals to v_in
+      // (it also means that join and v_out coincide)
+      if (old_rev_thread != v_in) {
+        _thread[old_rev_thread] = right;
+        _rev_thread[right] = old_rev_thread;
+      }
+
+      // Update _rev_thread using the new _thread values
+      for (int i = 0; i != int(_dirty_revs.size()); ++i) {
+        u = _dirty_revs[i];
+        _rev_thread[_thread[u]] = u;
+      }
+
+      // Update _pred, _forward, _last_succ and _succ_num for the
+      // stem nodes from u_out to u_in
+      int tmp_sc = 0, tmp_ls = _last_succ[u_out];
+      u = u_out;
+      while (u != u_in) {
+        w = _parent[u];
+        _pred[u] = _pred[w];
+        _forward[u] = !_forward[w];
+        tmp_sc += _succ_num[u] - _succ_num[w];
+        _succ_num[u] = tmp_sc;
+        _last_succ[w] = tmp_ls;
+        u = w;
+      }
+      _pred[u_in] = in_arc;
+      _forward[u_in] = (u_in == _source[in_arc]);
+      _succ_num[u_in] = old_succ_num;
+
+      // Set limits for updating _last_succ form v_in and v_out
+      // towards the root
+      int up_limit_in = -1;
+      int up_limit_out = -1;
+      if (_last_succ[join] == v_in) {
+        up_limit_out = join;
+      } else {
+        up_limit_in = join;
       }
 
       // Update _last_succ from v_in towards the root
-      int up_limit_out = _last_succ[join] == v_in ? join : -1;
-      int last_succ_out = _last_succ[u_out];
-      for (int u = v_in; u != -1 && _last_succ[u] == v_in; u = _parent[u]) {
-        _last_succ[u] = last_succ_out;
-      }
-
+      for (u = v_in; u != up_limit_in && _last_succ[u] == v_in;
+           u = _parent[u]) {
+        _last_succ[u] = _last_succ[u_out];
+      }
       // Update _last_succ from v_out towards the root
       if (join != old_rev_thread && v_in != old_rev_thread) {
-        for (int u = v_out; u != up_limit_out && _last_succ[u] == old_last_succ;
+        for (u = v_out; u != up_limit_out && _last_succ[u] == old_last_succ;
              u = _parent[u]) {
           _last_succ[u] = old_rev_thread;
         }
-      }
-      else if (last_succ_out != old_last_succ) {
-        for (int u = v_out; u != up_limit_out && _last_succ[u] == old_last_succ;
+      } else {
+        for (u = v_out; u != up_limit_out && _last_succ[u] == old_last_succ;
              u = _parent[u]) {
-          _last_succ[u] = last_succ_out;
+          _last_succ[u] = _last_succ[u_out];
         }
       }
 
       // Update _succ_num from v_in to join
-      for (int u = v_in; u != join; u = _parent[u]) {
+      for (u = v_in; u != join; u = _parent[u]) {
         _succ_num[u] += old_succ_num;
       }
       // Update _succ_num from v_out to join
-      for (int u = v_out; u != join; u = _parent[u]) {
+      for (u = v_out; u != join; u = _parent[u]) {
         _succ_num[u] -= old_succ_num;
       }
     }
 
-    // Update potentials in the subtree that has been moved
+    // Update potentials
     void updatePotential() {
-      Cost sigma = _pi[v_in] - _pi[u_in] -
-                   _pred_dir[u_in] * _cost[in_arc];
+      Cost sigma = _forward[u_in] ?
+        _pi[v_in] - _pi[u_in] - _cost[_pred[u_in]] :
+        _pi[v_in] - _pi[u_in] + _cost[_pred[u_in]];
+      // Update potentials in the subtree, which has been moved
       int end = _thread[_last_succ[u_in]];
       for (int u = u_in; u != end; u = _thread[u]) {