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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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Show white space 6 line context
... ...
@@ -175,3 +175,3 @@
175 175
    Value _delta;
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    int _phase_num;
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    int _factor;
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    IntVector _pred;
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@@ -515,8 +515,7 @@
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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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@@ -533,4 +532,5 @@
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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;
... ...
@@ -548,3 +548,3 @@
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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.
... ...
@@ -679,3 +679,3 @@
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    // Initialize the algorithm
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    ProblemType init(bool scaling) {
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    ProblemType init() {
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      if (_node_num == 0) return INFEASIBLE;
... ...
@@ -760,3 +760,3 @@
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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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@@ -772,5 +772,3 @@
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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) ;
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      } else {
... ...
@@ -813,4 +811,2 @@
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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);
... ...
@@ -889,4 +885,3 @@
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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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      }
Ignore white space 6 line context
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@@ -112,2 +112,6 @@
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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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@@ -161,2 +165,29 @@
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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    };
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  private:
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@@ -507,9 +538,8 @@
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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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    /// 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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@@ -525,7 +555,8 @@
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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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@@ -683,5 +714,2 @@
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      // Scaling factor
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      _alpha = 8;
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      // Check the sum of supply values
... ...
@@ -819,8 +847,17 @@
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    // Execute the algorithm and transform the results
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    void start(bool partial_augment) {
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    void start(Method method) {
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      // Maximum path length for partial augment
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      const int MAX_PATH_LENGTH = 4;
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      // Execute the algorithm
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      if (partial_augment) {
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        startPartialAugment();
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      } 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;
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      }
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@@ -853,5 +890,4 @@
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    /// Execute the algorithm performing partial augmentation and
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    /// relabel operations
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    void startPartialAugment() {
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    /// Execute the algorithm performing augment and relabel operations
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    void startAugment(int max_length = std::numeric_limits<int>::max()) {
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      // Paramters for heuristics
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@@ -859,4 +895,2 @@
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      const int BF_HEURISTIC_BOUND_FACTOR  = 3;
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      // Maximum augment path length
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      const int MAX_PATH_LENGTH = 4;
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@@ -927,3 +961,3 @@
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          while (_excess[tip] >= 0 &&
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                 int(path_nodes.size()) <= MAX_PATH_LENGTH) {
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                 int(path_nodes.size()) <= max_length) {
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            int u;
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@@ -986,3 +1020,3 @@
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    /// Execute the algorithm performing push and relabel operations
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    void startPushRelabel() {
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    void startPush() {
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      // Paramters for heuristics
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