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kpeter (Peter Kovacs)
kpeter@inf.elte.hu
More options for run() in scaling MCF algorithms (#180) - Three methods can be selected and the scaling factor can be given for CostScaling. - The scaling factor can be given for CapacityScaling.
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2 files changed with 71 insertions and 42 deletions:
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Ignore white space 4 line context
... ...
@@ -174,5 +174,5 @@
174 174

	
175 175
    Value _delta;
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    int _phase_num;
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    int _factor;
177 177
    IntVector _pred;
178 178

	
... ...
@@ -514,10 +514,9 @@
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    /// have to be set again. See \ref reset() for examples.
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    /// However the underlying digraph must not be modified after this
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    /// class have been constructed, since it copies the digraph.
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    /// class have been constructed, since it copies and extends the graph.
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    ///
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    /// \param scaling Enable or disable capacity scaling.
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    /// If the maximum upper bound and/or the amount of total supply
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    /// is rather small, the algorithm could be slightly faster without
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    /// scaling.
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    /// \param factor The capacity scaling factor. It must be larger than
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    /// one to use scaling. If it is less or equal to one, then scaling
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    /// will be disabled.
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    ///
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    /// \return \c INFEASIBLE if no feasible flow exists,
... ...
@@ -532,6 +531,7 @@
532 531
    ///
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    /// \see ProblemType
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    ProblemType run(bool scaling = true) {
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      ProblemType pt = init(scaling);
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    ProblemType run(int factor = 4) {
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      _factor = factor;
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      ProblemType pt = init();
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      if (pt != OPTIMAL) return pt;
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      return start();
... ...
@@ -547,5 +547,5 @@
547 547
    /// used, all the parameters given before are kept for the next
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    /// \ref run() call.
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    /// However the underlying digraph must not be modified after this
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    /// However, the underlying digraph must not be modified after this
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    /// class have been constructed, since it copies and extends the graph.
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    ///
... ...
@@ -678,5 +678,5 @@
678 678

	
679 679
    // Initialize the algorithm
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    ProblemType init(bool scaling) {
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    ProblemType init() {
681 681
      if (_node_num == 0) return INFEASIBLE;
682 682

	
... ...
@@ -759,5 +759,5 @@
759 759

	
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      // Initialize delta value
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      if (scaling) {
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      if (_factor > 1) {
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        // With scaling
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        Value max_sup = 0, max_dem = 0;
... ...
@@ -771,7 +771,5 @@
771 771
        }
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        max_sup = std::min(std::min(max_sup, max_dem), max_cap);
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        _phase_num = 0;
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        for (_delta = 1; 2 * _delta <= max_sup; _delta *= 2)
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          ++_phase_num;
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        for (_delta = 1; 2 * _delta <= max_sup; _delta *= 2) ;
776 774
      } else {
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        // Without scaling
... ...
@@ -812,6 +810,4 @@
812 810
      // Perform capacity scaling phases
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      int s, t;
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      int phase_cnt = 0;
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      int factor = 4;
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      ResidualDijkstra _dijkstra(*this);
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      while (true) {
... ...
@@ -888,6 +884,5 @@
888 884

	
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        if (_delta == 1) break;
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        if (++phase_cnt == _phase_num / 4) factor = 2;
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        _delta = _delta <= factor ? 1 : _delta / factor;
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        _delta = _delta <= _factor ? 1 : _delta / _factor;
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      }
893 888

	
Ignore white space 4 line context
... ...
@@ -111,4 +111,8 @@
111 111
  /// \warning This algorithm does not support negative costs for such
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  /// arcs that have infinite upper bound.
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  ///
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  /// \note %CostScaling provides three different internal methods,
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  /// from which the most efficient one is used by default.
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  /// For more information, see \ref Method.
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#ifdef DOXYGEN
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  template <typename GR, typename V, typename C, typename TR>
... ...
@@ -160,4 +164,31 @@
160 164
    };
161 165

	
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    /// \brief Constants for selecting the internal method.
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    ///
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    /// Enum type containing constants for selecting the internal method
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    /// for the \ref run() function.
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    ///
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    /// \ref CostScaling provides three internal methods that differ mainly
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    /// in their base operations, which are used in conjunction with the
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    /// relabel operation.
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    /// By default, the so called \ref PARTIAL_AUGMENT
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    /// "Partial Augment-Relabel" method is used, which proved to be
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    /// the most efficient and the most robust on various test inputs.
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    /// However, the other methods can be selected using the \ref run()
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    /// function with the proper parameter.
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    enum Method {
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      /// Local push operations are used, i.e. flow is moved only on one
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      /// admissible arc at once.
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      PUSH,
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      /// Augment operations are used, i.e. flow is moved on admissible
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      /// paths from a node with excess to a node with deficit.
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      AUGMENT,
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      /// Partial augment operations are used, i.e. flow is moved on 
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      /// admissible paths started from a node with excess, but the
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      /// lengths of these paths are limited. This method can be viewed
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      /// as a combined version of the previous two operations.
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      PARTIAL_AUGMENT
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    };
192

	
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  private:
163 194

	
... ...
@@ -506,11 +537,10 @@
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    /// \ref reset() is called, thus only the modified parameters
507 538
    /// have to be set again. See \ref reset() for examples.
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    /// However the underlying digraph must not be modified after this
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    /// class have been constructed, since it copies the digraph.
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    /// However, the underlying digraph must not be modified after this
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    /// class have been constructed, since it copies and extends the graph.
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    ///
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    /// \param partial_augment By default the algorithm performs
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    /// partial augment and relabel operations in the cost scaling
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    /// phases. Set this parameter to \c false for using local push and
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    /// relabel operations instead.
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    /// \param method The internal method that will be used in the
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    /// algorithm. For more information, see \ref Method.
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    /// \param factor The cost scaling factor. It must be larger than one.
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    ///
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    /// \return \c INFEASIBLE if no feasible flow exists,
... ...
@@ -524,9 +554,10 @@
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    /// these cases.
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    ///
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    /// \see ProblemType
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    ProblemType run(bool partial_augment = true) {
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    /// \see ProblemType, Method
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    ProblemType run(Method method = PARTIAL_AUGMENT, int factor = 8) {
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      _alpha = factor;
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      ProblemType pt = init();
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      if (pt != OPTIMAL) return pt;
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      start(partial_augment);
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      start(method);
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      return OPTIMAL;
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    }
... ...
@@ -682,7 +713,4 @@
682 713
      if (_res_node_num == 0) return INFEASIBLE;
683 714

	
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      // Scaling factor
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      _alpha = 8;
686

	
687 715
      // Check the sum of supply values
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      _sum_supply = 0;
... ...
@@ -818,10 +846,19 @@
818 846

	
819 847
    // Execute the algorithm and transform the results
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    void start(bool partial_augment) {
848
    void start(Method method) {
849
      // Maximum path length for partial augment
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      const int MAX_PATH_LENGTH = 4;
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821 852
      // Execute the algorithm
822
      if (partial_augment) {
823
        startPartialAugment();
824
      } else {
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        startPushRelabel();
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      switch (method) {
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        case PUSH:
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          startPush();
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          break;
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        case AUGMENT:
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          startAugment();
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          break;
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        case PARTIAL_AUGMENT:
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          startAugment(MAX_PATH_LENGTH);
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          break;
826 863
      }
827 864

	
... ...
@@ -852,12 +889,9 @@
852 889
    }
853 890

	
854
    /// Execute the algorithm performing partial augmentation and
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    /// relabel operations
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    void startPartialAugment() {
891
    /// Execute the algorithm performing augment and relabel operations
892
    void startAugment(int max_length = std::numeric_limits<int>::max()) {
857 893
      // Paramters for heuristics
858 894
      const int BF_HEURISTIC_EPSILON_BOUND = 1000;
859 895
      const int BF_HEURISTIC_BOUND_FACTOR  = 3;
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      // Maximum augment path length
861
      const int MAX_PATH_LENGTH = 4;
862 896

	
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      // Perform cost scaling phases
... ...
@@ -926,5 +960,5 @@
926 960
          int tip = start;
927 961
          while (_excess[tip] >= 0 &&
928
                 int(path_nodes.size()) <= MAX_PATH_LENGTH) {
962
                 int(path_nodes.size()) <= max_length) {
929 963
            int u;
930 964
            LargeCost min_red_cost, rc;
... ...
@@ -985,5 +1019,5 @@
985 1019

	
986 1020
    /// Execute the algorithm performing push and relabel operations
987
    void startPushRelabel() {
1021
    void startPush() {
988 1022
      // Paramters for heuristics
989 1023
      const int BF_HEURISTIC_EPSILON_BOUND = 1000;
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