LEMON/LEMON-main Changeset - r839:f3bc4e9b5f3a

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Changeset - r839:f3bc4e9b5f3a

« 823:a7e93d

840:2914b6 »

r839:f3bc4e9b5f3a

Sat, 20 Feb 2010 18:39:03

[Not Reviewed]

0 comments (0 inline)

kpeter (Peter Kovacs)
kpeter@inf.elte.hu

New heuristics for MCF algorithms (#340) and some implementation improvements. - A useful heuristic is added to NetworkSimplex to make the initial pivots faster. - A powerful global update heuristic is added to CostScaling and the implementation is reworked with various improvements. - Better relabeling in CostScaling to improve numerical stability and make the code faster. - A small improvement is made in CapacityScaling for better delta computation. - Add notes to the classes about the usage of vector<char> instead of vector<bool> for efficiency reasons.

0 4 0

default

4 files changed with 365 insertions and 149 deletions:

lemon/capacity_scaling.h

lemon/cost_scaling.h

235

119

lemon/cycle_canceling.h

lemon/network_simplex.h

118

↑ Collapse diff ↑

lemon/capacity_scaling.h

Show inline comments

@@ -134,9 +134,10 @@
 		    TEMPLATE_DIGRAPH_TYPEDEFS(GR);
 		    typedef std::vector<int> IntVector;
 		    typedef std::vector<char> BoolVector;
 		    typedef std::vector<Value> ValueVector;
 		    typedef std::vector<Cost> CostVector;
 		    typedef std::vector<char> BoolVector;
 		    // Note: vector<char> is used instead of vector<bool> for efficiency reasons
 		  private:
@@ -764,15 +765,15 @@
 		      // Initialize delta value
 		      if (_factor > 1) {
 		        // With scaling
 		        Value max_sup = 0, max_dem = 0;
 		        for (int i = 0; i != _node_num; ++i) {
 		        Value max_sup = 0, max_dem = 0, max_cap = 0;
 		        for (int i = 0; i != _root; ++i) {
 		          Value ex = _excess[i];
 		          if ( ex > max_sup) max_sup =  ex;
 		          if (-ex > max_dem) max_dem = -ex;
 		          int last_out = _first_out[i+1] - 1;
 		          for (int j = _first_out[i]; j != last_out; ++j) {
 		            if (_res_cap[j] > max_cap) max_cap = _res_cap[j];
+		        }
 		        Value max_cap = 0;
 		        for (int j = 0; j != _res_arc_num; ++j) {
 		          if (_res_cap[j] > max_cap) max_cap = _res_cap[j];
+		        }
 		        max_sup = std::min(std::min(max_sup, max_dem), max_cap);
 		        for (_delta = 1; 2 * _delta <= max_sup; _delta *= 2) ;

lemon/cost_scaling.h

Show inline comments

@@ -197,10 +197,11 @@
 		    TEMPLATE_DIGRAPH_TYPEDEFS(GR);
 		    typedef std::vector<int> IntVector;
 		    typedef std::vector<char> BoolVector;
 		    typedef std::vector<Value> ValueVector;
 		    typedef std::vector<Cost> CostVector;
 		    typedef std::vector<LargeCost> LargeCostVector;
 		    typedef std::vector<char> BoolVector;
 		    // Note: vector<char> is used instead of vector<bool> for efficiency reasons
 		  private:
@@ -244,6 +245,7 @@
 		    // Parameters of the problem
 		    bool _have_lower;
 		    Value _sum_supply;
 		    int _sup_node_num;
 		    // Data structures for storing the digraph
 		    IntNodeMap _node_id;
@@ -272,6 +274,12 @@
 		    LargeCost _epsilon;
 		    int _alpha;
 		    IntVector _buckets;
 		    IntVector _bucket_next;
 		    IntVector _bucket_prev;
 		    IntVector _rank;
 		    int _max_rank;
 		    // Data for a StaticDigraph structure
 		    typedef std::pair<int, int> IntPair;
 		    StaticDigraph _sgr;
@@ -802,6 +810,11 @@
+		        }
+		      }
 		      _sup_node_num = 0;
 		      for (NodeIt n(_graph); n != INVALID; ++n) {
 		        if (sup[n] > 0) ++_sup_node_num;
+		      }
 		      // Find a feasible flow using Circulation
 		      Circulation<Digraph, ConstMap<Arc, Value>, ValueArcMap, ValueNodeMap>
 		        circ(_graph, low, cap, sup);
@@ -836,7 +849,7 @@
+		        }
 		        for (int a = _first_out[_root]; a != _res_arc_num; ++a) {
 		          int ra = _reverse[a];
-		          _res_cap[a] = 1;
+		          _res_cap[a] = 0;
 		          _res_cap[ra] = 0;
 		          _cost[a] = 0;
 		          _cost[ra] = 0;
@@ -851,6 +864,13 @@
 		      // Maximum path length for partial augment
 		      const int MAX_PATH_LENGTH = 4;
 		      // Initialize data structures for buckets
 		      _max_rank = _alpha * _res_node_num;
 		      _buckets.resize(_max_rank);
 		      _bucket_next.resize(_res_node_num + 1);
 		      _bucket_prev.resize(_res_node_num + 1);
 		      _rank.resize(_res_node_num + 1);
 		      // Execute the algorithm
 		      switch (method) {
 		        case PUSH:
@@ -890,51 +910,23 @@
+		      }
+		    }
 		    /// Execute the algorithm performing augment and relabel operations
 		    void startAugment(int max_length = std::numeric_limits<int>::max()) {
 		      // Paramters for heuristics
 		      const int BF_HEURISTIC_EPSILON_BOUND = 1000;
 		      const int BF_HEURISTIC_BOUND_FACTOR  = 3;
 		      // Perform cost scaling phases
 		      IntVector pred_arc(_res_node_num);
 		      std::vector<int> path_nodes;
 		      for ( ; _epsilon >= 1; _epsilon = _epsilon < _alpha && _epsilon > 1 ?
 : _epsilon / _alpha )
+		      {
 		        // "Early Termination" heuristic: use Bellman-Ford algorithm
 		        // to check if the current flow is optimal
 		        if (_epsilon <= BF_HEURISTIC_EPSILON_BOUND) {
 		          _arc_vec.clear();
 		          _cost_vec.clear();
 		          for (int j = 0; j != _res_arc_num; ++j) {
 		            if (_res_cap[j] > 0) {
 		              _arc_vec.push_back(IntPair(_source[j], _target[j]));
 		              _cost_vec.push_back(_cost[j] + 1);
+		            }
+		          }
 		          _sgr.build(_res_node_num, _arc_vec.begin(), _arc_vec.end());
 		          BellmanFord<StaticDigraph, LargeCostArcMap> bf(_sgr, _cost_map);
 		          bf.init(0);
 		          bool done = false;
 		          int K = int(BF_HEURISTIC_BOUND_FACTOR * sqrt(_res_node_num));
 		          for (int i = 0; i < K && !done; ++i)
 		            done = bf.processNextWeakRound();
 		          if (done) break;
+		        }
 		    // Initialize a cost scaling phase
 		    void initPhase() {
 		        // Saturate arcs not satisfying the optimality condition
 		        for (int a = 0; a != _res_arc_num; ++a) {
 		          if (_res_cap[a] > 0 &&
-		              _cost[a] + _pi[_source[a]] - _pi[_target[a]] < 0) {
+		      for (int u = 0; u != _res_node_num; ++u) {
 		        int last_out = _first_out[u+1];
 		        LargeCost pi_u = _pi[u];
 		        for (int a = _first_out[u]; a != last_out; ++a) {
 		          int v = _target[a];
 		          if (_res_cap[a] > 0 && _cost[a] + pi_u - _pi[v] < 0) {
 		            Value delta = _res_cap[a];
 		            _excess[_source[a]] -= delta;
 		            _excess[_target[a]] += delta;
 		            _excess[u] -= delta;
 		            _excess[v] += delta;
 		            _res_cap[a] = 0;
 		            _res_cap[_reverse[a]] += delta;
+		          }
+		        }
+		      }
 		        // Find active nodes (i.e. nodes with positive excess)
 		        for (int u = 0; u != _res_node_num; ++u) {
@@ -945,6 +937,146 @@
 		        for (int u = 0; u != _res_node_num; ++u) {
 		          _next_out[u] = _first_out[u];
+		        }
+		    }
 		    // Early termination heuristic
 		    bool earlyTermination() {
 		      const double EARLY_TERM_FACTOR = 3.0;
 		      // Build a static residual graph
 		      _arc_vec.clear();
 		      _cost_vec.clear();
 		      for (int j = 0; j != _res_arc_num; ++j) {
 		        if (_res_cap[j] > 0) {
 		          _arc_vec.push_back(IntPair(_source[j], _target[j]));
 		          _cost_vec.push_back(_cost[j] + 1);
+		        }
+		      }
 		      _sgr.build(_res_node_num, _arc_vec.begin(), _arc_vec.end());
 		      // Run Bellman-Ford algorithm to check if the current flow is optimal
 		      BellmanFord<StaticDigraph, LargeCostArcMap> bf(_sgr, _cost_map);
 		      bf.init(0);
 		      bool done = false;
 		      int K = int(EARLY_TERM_FACTOR * std::sqrt(double(_res_node_num)));
 		      for (int i = 0; i < K && !done; ++i) {
 		        done = bf.processNextWeakRound();
+		      }
 		      return done;
+		    }
 		    // Global potential update heuristic
 		    void globalUpdate() {
 		      int bucket_end = _root + 1;
 		      // Initialize buckets
 		      for (int r = 0; r != _max_rank; ++r) {
 		        _buckets[r] = bucket_end;
+		      }
 		      Value total_excess = 0;
 		      for (int i = 0; i != _res_node_num; ++i) {
 		        if (_excess[i] < 0) {
 		          _rank[i] = 0;
 		          _bucket_next[i] = _buckets[0];
 		          _bucket_prev[_buckets[0]] = i;
 		          _buckets[0] = i;
 		        } else {
 		          total_excess += _excess[i];
 		          _rank[i] = _max_rank;
+		        }
+		      }
 		      if (total_excess == 0) return;
 		      // Search the buckets
 		      int r = 0;
 		      for ( ; r != _max_rank; ++r) {
 		        while (_buckets[r] != bucket_end) {
 		          // Remove the first node from the current bucket
 		          int u = _buckets[r];
 		          _buckets[r] = _bucket_next[u];
 		          // Search the incomming arcs of u
 		          LargeCost pi_u = _pi[u];
 		          int last_out = _first_out[u+1];
 		          for (int a = _first_out[u]; a != last_out; ++a) {
 		            int ra = _reverse[a];
 		            if (_res_cap[ra] > 0) {
 		              int v = _source[ra];
 		              int old_rank_v = _rank[v];
 		              if (r < old_rank_v) {
 		                // Compute the new rank of v
 		                LargeCost nrc = (_cost[ra] + _pi[v] - pi_u) / _epsilon;
 		                int new_rank_v = old_rank_v;
 		                if (nrc < LargeCost(_max_rank))
 		                  new_rank_v = r + 1 + int(nrc);
 		                // Change the rank of v
 		                if (new_rank_v < old_rank_v) {
 		                  _rank[v] = new_rank_v;
 		                  _next_out[v] = _first_out[v];
 		                  // Remove v from its old bucket
 		                  if (old_rank_v < _max_rank) {
 		                    if (_buckets[old_rank_v] == v) {
 		                      _buckets[old_rank_v] = _bucket_next[v];
 		                    } else {
 		                      _bucket_next[_bucket_prev[v]] = _bucket_next[v];
 		                      _bucket_prev[_bucket_next[v]] = _bucket_prev[v];
+		                    }
+		                  }
 		                  // Insert v to its new bucket
 		                  _bucket_next[v] = _buckets[new_rank_v];
 		                  _bucket_prev[_buckets[new_rank_v]] = v;
 		                  _buckets[new_rank_v] = v;
+		                }
+		              }
+		            }
+		          }
 		          // Finish search if there are no more active nodes
 		          if (_excess[u] > 0) {
 		            total_excess -= _excess[u];
 		            if (total_excess <= 0) break;
+		          }
+		        }
 		        if (total_excess <= 0) break;
+		      }
 		      // Relabel nodes
 		      for (int u = 0; u != _res_node_num; ++u) {
 		        int k = std::min(_rank[u], r);
 		        if (k > 0) {
 		          _pi[u] -= _epsilon * k;
 		          _next_out[u] = _first_out[u];
+		        }
+		      }
+		    }
 		    /// Execute the algorithm performing augment and relabel operations
 		    void startAugment(int max_length = std::numeric_limits<int>::max()) {
 		      // Paramters for heuristics
 		      const int EARLY_TERM_EPSILON_LIMIT = 1000;
 		      const double GLOBAL_UPDATE_FACTOR = 3.0;
 		      const int global_update_freq = int(GLOBAL_UPDATE_FACTOR *
 		        (_res_node_num + _sup_node_num * _sup_node_num));
 		      int next_update_limit = global_update_freq;
 		      int relabel_cnt = 0;
 		      // Perform cost scaling phases
 		      std::vector<int> path;
 		      for ( ; _epsilon >= 1; _epsilon = _epsilon < _alpha && _epsilon > 1 ?
 : _epsilon / _alpha )
+		      {
 		        // Early termination heuristic
 		        if (_epsilon <= EARLY_TERM_EPSILON_LIMIT) {
 		          if (earlyTermination()) break;
+		        }
 		        // Initialize current phase
 		        initPhase();
 		        // Perform partial augment and relabel operations
 		        while (true) {
@@ -955,46 +1087,44 @@
+		          }
 		          if (_active_nodes.size() == 0) break;
 		          int start = _active_nodes.front();
 		          path_nodes.clear();
 		          path_nodes.push_back(start);
 		          // Find an augmenting path from the start node
 		          path.clear();
 		          int tip = start;
 		          while (_excess[tip] >= 0 &&
 		                 int(path_nodes.size()) <= max_length) {
 		          while (_excess[tip] >= 0 && int(path.size()) < max_length) {
 		            int u;
 		            LargeCost min_red_cost, rc;
 		            int last_out = _sum_supply < 0 ?
-		              _first_out[tip+1] : _first_out[tip+1] - 1;
+		            LargeCost min_red_cost, rc, pi_tip = _pi[tip];
 		            int last_out = _first_out[tip+1];
 		            for (int a = _next_out[tip]; a != last_out; ++a) {
 		              if (_res_cap[a] > 0 &&
 		                  _cost[a] + _pi[_source[a]] - _pi[_target[a]] < 0) {
 		                u = _target[a];
-		                pred_arc[u] = a;
+		              if (_res_cap[a] > 0 && _cost[a] + pi_tip - _pi[u] < 0) {
 		                path.push_back(a);
 		                _next_out[tip] = a;
 		                tip = u;
 		                path_nodes.push_back(tip);
 		                goto next_step;
+		              }
+		            }
 		            // Relabel tip node
-		            min_red_cost = std::numeric_limits<LargeCost>::max() / 2;
 		            min_red_cost = std::numeric_limits<LargeCost>::max();
 		            if (tip != start) {
 		              int ra = _reverse[path.back()];
 		              min_red_cost = _cost[ra] + pi_tip - _pi[_target[ra]];
+		            }
 		            for (int a = _first_out[tip]; a != last_out; ++a) {
-		              rc = _cost[a] + _pi[_source[a]] - _pi[_target[a]];
+		              rc = _cost[a] + pi_tip - _pi[_target[a]];
 		              if (_res_cap[a] > 0 && rc < min_red_cost) {
 		                min_red_cost = rc;
+		              }
+		            }
 		            _pi[tip] -= min_red_cost + _epsilon;
 		            // Reset the next arc of tip
 		            _next_out[tip] = _first_out[tip];
 		            ++relabel_cnt;
 		            // Step back
 		            if (tip != start) {
 		              path_nodes.pop_back();
 		              tip = path_nodes.back();
 		              tip = _source[path.back()];
 		              path.pop_back();
+		            }
 		          next_step: ;
@@ -1002,11 +1132,11 @@
 		          // Augment along the found path (as much flow as possible)
 		          Value delta;
 		          int u, v = path_nodes.front(), pa;
 		          for (int i = 1; i < int(path_nodes.size()); ++i) {
 		          int pa, u, v = start;
 		          for (int i = 0; i != int(path.size()); ++i) {
 		            pa = path[i];
 		            u = v;
 		            v = path_nodes[i];
 		            pa = pred_arc[v];
 		            v = _target[pa];
 		            delta = std::min(_res_cap[pa], _excess[u]);
 		            _res_cap[pa] -= delta;
 		            _res_cap[_reverse[pa]] += delta;
@@ -1015,6 +1145,12 @@
 		            if (_excess[v] > 0 && _excess[v] <= delta)
 		              _active_nodes.push_back(v);
+		          }
 		          // Global update heuristic
 		          if (relabel_cnt >= next_update_limit) {
 		            globalUpdate();
 		            next_update_limit += global_update_freq;
+		          }
+		        }
+		      }
+		    }
@@ -1022,98 +1158,70 @@
 		    /// Execute the algorithm performing push and relabel operations
 		    void startPush() {
 		      // Paramters for heuristics
 		      const int BF_HEURISTIC_EPSILON_BOUND = 1000;
 		      const int BF_HEURISTIC_BOUND_FACTOR  = 3;
 		      const int EARLY_TERM_EPSILON_LIMIT = 1000;
 		      const double GLOBAL_UPDATE_FACTOR = 2.0;
 		      const int global_update_freq = int(GLOBAL_UPDATE_FACTOR *
 		        (_res_node_num + _sup_node_num * _sup_node_num));
 		      int next_update_limit = global_update_freq;
 		      int relabel_cnt = 0;
 		      // Perform cost scaling phases
 		      BoolVector hyper(_res_node_num, false);
 		      LargeCostVector hyper_cost(_res_node_num);
 		      for ( ; _epsilon >= 1; _epsilon = _epsilon < _alpha && _epsilon > 1 ?
 : _epsilon / _alpha )
+		      {
 		        // "Early Termination" heuristic: use Bellman-Ford algorithm
 		        // to check if the current flow is optimal
 		        if (_epsilon <= BF_HEURISTIC_EPSILON_BOUND) {
 		          _arc_vec.clear();
 		          _cost_vec.clear();
 		          for (int j = 0; j != _res_arc_num; ++j) {
 		            if (_res_cap[j] > 0) {
 		              _arc_vec.push_back(IntPair(_source[j], _target[j]));
 		              _cost_vec.push_back(_cost[j] + 1);
+		            }
+		          }
 		          _sgr.build(_res_node_num, _arc_vec.begin(), _arc_vec.end());
 		          BellmanFord<StaticDigraph, LargeCostArcMap> bf(_sgr, _cost_map);
 		          bf.init(0);
 		          bool done = false;
 		          int K = int(BF_HEURISTIC_BOUND_FACTOR * sqrt(_res_node_num));
 		          for (int i = 0; i < K && !done; ++i)
 		            done = bf.processNextWeakRound();
 		          if (done) break;
 		        // Early termination heuristic
 		        if (_epsilon <= EARLY_TERM_EPSILON_LIMIT) {
 		          if (earlyTermination()) break;
+		        }
 		        // Saturate arcs not satisfying the optimality condition
 		        for (int a = 0; a != _res_arc_num; ++a) {
 		          if (_res_cap[a] > 0 &&
 		              _cost[a] + _pi[_source[a]] - _pi[_target[a]] < 0) {
 		            Value delta = _res_cap[a];
 		            _excess[_source[a]] -= delta;
 		            _excess[_target[a]] += delta;
 		            _res_cap[a] = 0;
 		            _res_cap[_reverse[a]] += delta;
+		          }
+		        }
 		        // Find active nodes (i.e. nodes with positive excess)
 		        for (int u = 0; u != _res_node_num; ++u) {
 		          if (_excess[u] > 0) _active_nodes.push_back(u);
+		        }
 		        // Initialize the next arcs
 		        for (int u = 0; u != _res_node_num; ++u) {
 		          _next_out[u] = _first_out[u];
+		        }
+		        // Initialize current phase
 		        initPhase();
 		        // Perform push and relabel operations
 		        while (_active_nodes.size() > 0) {
 		          LargeCost min_red_cost, rc;
+		          LargeCost min_red_cost, rc, pi_n;
 		          Value delta;
 		          int n, t, a, last_out = _res_arc_num;
 		        next_node:
 		          // Select an active node (FIFO selection)
 		        next_node:
 		          n = _active_nodes.front();
 		          last_out = _sum_supply < 0 ?
 		            _first_out[n+1] : _first_out[n+1] - 1;
 		          last_out = _first_out[n+1];
 		          pi_n = _pi[n];
 		          // Perform push operations if there are admissible arcs
 		          if (_excess[n] > 0) {
 		            for (a = _next_out[n]; a != last_out; ++a) {
 		              if (_res_cap[a] > 0 &&
-		                  _cost[a] + _pi[_source[a]] - _pi[_target[a]] < 0) {
+		                  _cost[a] + pi_n - _pi[_target[a]] < 0) {
 		                delta = std::min(_res_cap[a], _excess[n]);
 		                t = _target[a];
 		                // Push-look-ahead heuristic
 		                Value ahead = -_excess[t];
 		                int last_out_t = _sum_supply < 0 ?
 		                  _first_out[t+1] : _first_out[t+1] - 1;
 		                int last_out_t = _first_out[t+1];
 		                LargeCost pi_t = _pi[t];
 		                for (int ta = _next_out[t]; ta != last_out_t; ++ta) {
 		                  if (_res_cap[ta] > 0 &&
-		                      _cost[ta] + _pi[_source[ta]] - _pi[_target[ta]] < 0)
+		                      _cost[ta] + pi_t - _pi[_target[ta]] < 0)
 		                    ahead += _res_cap[ta];
 		                  if (ahead >= delta) break;
+		                }
 		                if (ahead < 0) ahead = 0;
 		                // Push flow along the arc
 		                if (ahead < delta) {
+		                if (ahead < delta && !hyper[t]) {
 		                  _res_cap[a] -= ahead;
 		                  _res_cap[_reverse[a]] += ahead;
 		                  _excess[n] -= ahead;
 		                  _excess[t] += ahead;
 		                  _active_nodes.push_front(t);
 		                  hyper[t] = true;
 		                  hyper_cost[t] = _cost[a] + pi_n - pi_t;
 		                  _next_out[n] = a;
 		                  goto next_node;
 		                } else {
@@ -1136,18 +1244,18 @@
 		          // Relabel the node if it is still active (or hyper)
 		          if (_excess[n] > 0 || hyper[n]) {
-		            min_red_cost = std::numeric_limits<LargeCost>::max() / 2;
+		             min_red_cost = hyper[n] ? -hyper_cost[n] :
 		               std::numeric_limits<LargeCost>::max();
 		            for (int a = _first_out[n]; a != last_out; ++a) {
-		              rc = _cost[a] + _pi[_source[a]] - _pi[_target[a]];
+		              rc = _cost[a] + pi_n - _pi[_target[a]];
 		              if (_res_cap[a] > 0 && rc < min_red_cost) {
 		                min_red_cost = rc;
+		              }
+		            }
 		            _pi[n] -= min_red_cost + _epsilon;
 		            _next_out[n] = _first_out[n];
 		            hyper[n] = false;
 		            // Reset the next arc
-		            _next_out[n] = _first_out[n];
+		            ++relabel_cnt;
+		          }
 		          // Remove nodes that are not active nor hyper
@@ -1157,6 +1265,14 @@
 		                  !hyper[_active_nodes.front()] ) {
 		            _active_nodes.pop_front();
+		          }
 		          // Global update heuristic
 		          if (relabel_cnt >= next_update_limit) {
 		            globalUpdate();
 		            for (int u = 0; u != _res_node_num; ++u)
 		              hyper[u] = false;
 		            next_update_limit += global_update_freq;
+		          }
+		        }
+		      }
+		    }

lemon/cycle_canceling.h

Show inline comments

@@ -144,10 +144,11 @@
 		    TEMPLATE_DIGRAPH_TYPEDEFS(GR);
 		    typedef std::vector<int> IntVector;
 		    typedef std::vector<char> CharVector;
 		    typedef std::vector<double> DoubleVector;
 		    typedef std::vector<Value> ValueVector;
 		    typedef std::vector<Cost> CostVector;
 		    typedef std::vector<char> BoolVector;
 		    // Note: vector<char> is used instead of vector<bool> for efficiency reasons
 		  private:
@@ -198,7 +199,7 @@
 		    IntArcMap _arc_idf;
 		    IntArcMap _arc_idb;
 		    IntVector _first_out;
-		    CharVector _forward;
+		    BoolVector _forward;
 		    IntVector _source;
 		    IntVector _target;
 		    IntVector _reverse;
@@ -933,8 +934,8 @@
 		      // Contruct auxiliary data vectors
 		      DoubleVector pi(_res_node_num, 0.0);
 		      IntVector level(_res_node_num);
 		      CharVector reached(_res_node_num);
 		      CharVector processed(_res_node_num);
 		      BoolVector reached(_res_node_num);
 		      BoolVector processed(_res_node_num);
 		      IntVector pred_node(_res_node_num);
 		      IntVector pred_arc(_res_node_num);
 		      std::vector<int> stack(_res_node_num);

lemon/network_simplex.h

Show inline comments

@@ -164,9 +164,10 @@
 		    TEMPLATE_DIGRAPH_TYPEDEFS(GR);
 		    typedef std::vector<int> IntVector;
 		    typedef std::vector<char> CharVector;
 		    typedef std::vector<Value> ValueVector;
 		    typedef std::vector<Cost> CostVector;
 		    typedef std::vector<char> BoolVector;
 		    // Note: vector<char> is used instead of vector<bool> for efficiency reasons
 		    // State constants for arcs
 		    enum ArcStateEnum {
@@ -212,8 +213,8 @@
 		    IntVector _succ_num;
 		    IntVector _last_succ;
 		    IntVector _dirty_revs;
 		    CharVector _forward;
 		    CharVector _state;
 		    BoolVector _forward;
 		    BoolVector _state;
 		    int _root;
 		    // Temporary data used in the current pivot iteration
@@ -244,7 +245,7 @@
 		      const IntVector  &_source;
 		      const IntVector  &_target;
 		      const CostVector &_cost;
-		      const CharVector &_state;
+		      const BoolVector &_state;
 		      const CostVector &_pi;
 		      int &_in_arc;
 		      int _search_arc_num;
@@ -265,7 +266,7 @@
 		      // Find next entering arc
 		      bool findEnteringArc() {
 		        Cost c;
-		        for (int e = _next_arc; e < _search_arc_num; ++e) {
+		        for (int e = _next_arc; e != _search_arc_num; ++e) {
 		          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (c < 0) {
 		            _in_arc = e;
@@ -273,7 +274,7 @@
 		            return true;
+		          }
+		        }
-		        for (int e = 0; e < _next_arc; ++e) {
+		        for (int e = 0; e != _next_arc; ++e) {
 		          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (c < 0) {
 		            _in_arc = e;
@@ -296,7 +297,7 @@
 		      const IntVector  &_source;
 		      const IntVector  &_target;
 		      const CostVector &_cost;
-		      const CharVector &_state;
+		      const BoolVector &_state;
 		      const CostVector &_pi;
 		      int &_in_arc;
 		      int _search_arc_num;
@@ -313,7 +314,7 @@
 		      // Find next entering arc
 		      bool findEnteringArc() {
 		        Cost c, min = 0;
-		        for (int e = 0; e < _search_arc_num; ++e) {
+		        for (int e = 0; e != _search_arc_num; ++e) {
 		          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (c < min) {
 		            min = c;
@@ -335,7 +336,7 @@
 		      const IntVector  &_source;
 		      const IntVector  &_target;
 		      const CostVector &_cost;
-		      const CharVector &_state;
+		      const BoolVector &_state;
 		      const CostVector &_pi;
 		      int &_in_arc;
 		      int _search_arc_num;
@@ -354,7 +355,7 @@
 		        _next_arc(0)
+		      {
 		        // The main parameters of the pivot rule
-		        const double BLOCK_SIZE_FACTOR = 0.5;
+		        const double BLOCK_SIZE_FACTOR = 1.0;
 		        const int MIN_BLOCK_SIZE = 10;
 		        _block_size = std::max( int(BLOCK_SIZE_FACTOR *
@@ -367,7 +368,7 @@
 		        Cost c, min = 0;
 		        int cnt = _block_size;
 		        int e;
-		        for (e = _next_arc; e < _search_arc_num; ++e) {
+		        for (e = _next_arc; e != _search_arc_num; ++e) {
 		          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (c < min) {
 		            min = c;
@@ -378,7 +379,7 @@
 		            cnt = _block_size;
+		          }
+		        }
-		        for (e = 0; e < _next_arc; ++e) {
+		        for (e = 0; e != _next_arc; ++e) {
 		          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (c < min) {
 		            min = c;
@@ -408,7 +409,7 @@
 		      const IntVector  &_source;
 		      const IntVector  &_target;
 		      const CostVector &_cost;
-		      const CharVector &_state;
+		      const BoolVector &_state;
 		      const CostVector &_pi;
 		      int &_in_arc;
 		      int _search_arc_num;
@@ -469,7 +470,7 @@
 		        // Major iteration: build a new candidate list
 		        min = 0;
 		        _curr_length = 0;
-		        for (e = _next_arc; e < _search_arc_num; ++e) {
+		        for (e = _next_arc; e != _search_arc_num; ++e) {
 		          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (c < 0) {
 		            _candidates[_curr_length++] = e;
@@ -480,7 +481,7 @@
 		            if (_curr_length == _list_length) goto search_end;
+		          }
+		        }
-		        for (e = 0; e < _next_arc; ++e) {
+		        for (e = 0; e != _next_arc; ++e) {
 		          c = _state[e] * (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (c < 0) {
 		            _candidates[_curr_length++] = e;
@@ -511,7 +512,7 @@
 		      const IntVector  &_source;
 		      const IntVector  &_target;
 		      const CostVector &_cost;
-		      const CharVector &_state;
+		      const BoolVector &_state;
 		      const CostVector &_pi;
 		      int &_in_arc;
 		      int _search_arc_num;
@@ -564,7 +565,7 @@
 		      bool findEnteringArc() {
 		        // Check the current candidate list
 		        int e;
-		        for (int i = 0; i < _curr_length; ++i) {
+		        for (int i = 0; i != _curr_length; ++i) {
 		          e = _candidates[i];
 		          _cand_cost[e] = _state[e] *
 		            (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
@@ -577,7 +578,7 @@
 		        int cnt = _block_size;
 		        int limit = _head_length;
-		        for (e = _next_arc; e < _search_arc_num; ++e) {
+		        for (e = _next_arc; e != _search_arc_num; ++e) {
 		          _cand_cost[e] = _state[e] *
 		            (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (_cand_cost[e] < 0) {
@@ -589,7 +590,7 @@
 		            cnt = _block_size;
+		          }
+		        }
-		        for (e = 0; e < _next_arc; ++e) {
+		        for (e = 0; e != _next_arc; ++e) {
 		          _cand_cost[e] = _state[e] *
 		            (_cost[e] + _pi[_source[e]] - _pi[_target[e]]);
 		          if (_cand_cost[e] < 0) {
@@ -1328,7 +1329,7 @@
+		      }
 		      // Update _rev_thread using the new _thread values
-		      for (int i = 0; i < int(_dirty_revs.size()); ++i) {
+		      for (int i = 0; i != int(_dirty_revs.size()); ++i) {
 		        u = _dirty_revs[i];
 		        _rev_thread[_thread[u]] = u;
+		      }
@@ -1400,6 +1401,100 @@
+		      }
+		    }
 		    // Heuristic initial pivots
 		    bool initialPivots() {
 		      Value curr, total = 0;
 		      std::vector<Node> supply_nodes, demand_nodes;
 		      for (NodeIt u(_graph); u != INVALID; ++u) {
 		        curr = _supply[_node_id[u]];
 		        if (curr > 0) {
 		          total += curr;
 		          supply_nodes.push_back(u);
+		        }
 		        else if (curr < 0) {
 		          demand_nodes.push_back(u);
+		        }
+		      }
 		      if (_sum_supply > 0) total -= _sum_supply;
 		      if (total <= 0) return true;
 		      IntVector arc_vector;
 		      if (_sum_supply >= 0) {
 		        if (supply_nodes.size() == 1 && demand_nodes.size() == 1) {
 		          // Perform a reverse graph search from the sink to the source
 		          typename GR::template NodeMap<bool> reached(_graph, false);
 		          Node s = supply_nodes[0], t = demand_nodes[0];
 		          std::vector<Node> stack;
 		          reached[t] = true;
 		          stack.push_back(t);
 		          while (!stack.empty()) {
 		            Node u, v = stack.back();
 		            stack.pop_back();
 		            if (v == s) break;
 		            for (InArcIt a(_graph, v); a != INVALID; ++a) {
 		              if (reached[u = _graph.source(a)]) continue;
 		              int j = _arc_id[a];
 		              if (_cap[j] >= total) {
 		                arc_vector.push_back(j);
 		                reached[u] = true;
 		                stack.push_back(u);
+		              }
+		            }
+		          }
 		        } else {
 		          // Find the min. cost incomming arc for each demand node
 		          for (int i = 0; i != int(demand_nodes.size()); ++i) {
 		            Node v = demand_nodes[i];
 		            Cost c, min_cost = std::numeric_limits<Cost>::max();
 		            Arc min_arc = INVALID;
 		            for (InArcIt a(_graph, v); a != INVALID; ++a) {
 		              c = _cost[_arc_id[a]];
 		              if (c < min_cost) {
 		                min_cost = c;
 		                min_arc = a;
+		              }
+		            }
 		            if (min_arc != INVALID) {
 		              arc_vector.push_back(_arc_id[min_arc]);
+		            }
+		          }
+		        }
 		      } else {
 		        // Find the min. cost outgoing arc for each supply node
 		        for (int i = 0; i != int(supply_nodes.size()); ++i) {
 		          Node u = supply_nodes[i];
 		          Cost c, min_cost = std::numeric_limits<Cost>::max();
 		          Arc min_arc = INVALID;
 		          for (OutArcIt a(_graph, u); a != INVALID; ++a) {
 		            c = _cost[_arc_id[a]];
 		            if (c < min_cost) {
 		              min_cost = c;
 		              min_arc = a;
+		            }
+		          }
 		          if (min_arc != INVALID) {
 		            arc_vector.push_back(_arc_id[min_arc]);
+		          }
+		        }
+		      }
 		      // Perform heuristic initial pivots
 		      for (int i = 0; i != int(arc_vector.size()); ++i) {
 		        in_arc = arc_vector[i];
 		        if (_state[in_arc] * (_cost[in_arc] + _pi[_source[in_arc]] -
 		            _pi[_target[in_arc]]) >= 0) continue;
 		        findJoinNode();
 		        bool change = findLeavingArc();
 		        if (delta >= MAX) return false;
 		        changeFlow(change);
 		        if (change) {
 		          updateTreeStructure();
 		          updatePotential();
+		        }
+		      }
 		      return true;
+		    }
 		    // Execute the algorithm
 		    ProblemType start(PivotRule pivot_rule) {
 		      // Select the pivot rule implementation
@@ -1422,6 +1517,9 @@
 		    ProblemType start() {
 		      PivotRuleImpl pivot(*this);
 		      // Perform heuristic initial pivots
 		      if (!initialPivots()) return UNBOUNDED;
 		      // Execute the Network Simplex algorithm
 		      while (pivot.findEnteringArc()) {
 		        findJoinNode();

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