Changeset 876:3b53491bf643 in lemon for lemon/cost_scaling.h

Ignore:
Timestamp:
11/12/09 23:34:35 (11 years ago)
Branch:
default
Phase:
public
Rebase:
31306464373530663736663634663865303635326136663934636335303533383063623764626530
Message:

More options for run() in scaling MCF algorithms (#180)

File:
1 edited

Unmodified
Removed
• lemon/cost_scaling.h

 r875 /// \warning This algorithm does not support negative costs for such /// arcs that have infinite upper bound. /// /// \note %CostScaling provides three different internal methods, /// from which the most efficient one is used by default. /// For more information, see \ref Method. #ifdef DOXYGEN template }; /// \brief Constants for selecting the internal method. /// /// Enum type containing constants for selecting the internal method /// for the \ref run() function. /// /// \ref CostScaling provides three internal methods that differ mainly /// in their base operations, which are used in conjunction with the /// relabel operation. /// By default, the so called \ref PARTIAL_AUGMENT /// "Partial Augment-Relabel" method is used, which proved to be /// the most efficient and the most robust on various test inputs. /// However, the other methods can be selected using the \ref run() /// function with the proper parameter. enum Method { /// Local push operations are used, i.e. flow is moved only on one /// admissible arc at once. PUSH, /// Augment operations are used, i.e. flow is moved on admissible /// paths from a node with excess to a node with deficit. AUGMENT, /// Partial augment operations are used, i.e. flow is moved on /// admissible paths started from a node with excess, but the /// lengths of these paths are limited. This method can be viewed /// as a combined version of the previous two operations. PARTIAL_AUGMENT }; private: /// \ref reset() is called, thus only the modified parameters /// have to be set again. See \ref reset() for examples. /// However the underlying digraph must not be modified after this /// class have been constructed, since it copies the digraph. /// /// \param partial_augment By default the algorithm performs /// partial augment and relabel operations in the cost scaling /// phases. Set this parameter to \c false for using local push and /// relabel operations instead. /// However, the underlying digraph must not be modified after this /// class have been constructed, since it copies and extends the graph. /// /// \param method The internal method that will be used in the /// algorithm. For more information, see \ref Method. /// \param factor The cost scaling factor. It must be larger than one. /// /// \return \c INFEASIBLE if no feasible flow exists, /// these cases. /// /// \see ProblemType ProblemType run(bool partial_augment = true) { /// \see ProblemType, Method ProblemType run(Method method = PARTIAL_AUGMENT, int factor = 8) { _alpha = factor; ProblemType pt = init(); if (pt != OPTIMAL) return pt; start(partial_augment); start(method); return OPTIMAL; } ProblemType init() { if (_res_node_num == 0) return INFEASIBLE; // Scaling factor _alpha = 8; // Check the sum of supply values // Execute the algorithm and transform the results void start(bool partial_augment) { void start(Method method) { // Maximum path length for partial augment const int MAX_PATH_LENGTH = 4; // Execute the algorithm if (partial_augment) { startPartialAugment(); } else { startPushRelabel(); switch (method) { case PUSH: startPush(); break; case AUGMENT: startAugment(); break; case PARTIAL_AUGMENT: startAugment(MAX_PATH_LENGTH); break; } } /// Execute the algorithm performing partial augmentation and /// relabel operations void startPartialAugment() { /// Execute the algorithm performing augment and relabel operations void startAugment(int max_length = std::numeric_limits::max()) { // Paramters for heuristics const int BF_HEURISTIC_EPSILON_BOUND = 1000; const int BF_HEURISTIC_BOUND_FACTOR  = 3; // Maximum augment path length const int MAX_PATH_LENGTH = 4; // Perform cost scaling phases int tip = start; while (_excess[tip] >= 0 && int(path_nodes.size()) <= MAX_PATH_LENGTH) { int(path_nodes.size()) <= max_length) { int u; LargeCost min_red_cost, rc; /// Execute the algorithm performing push and relabel operations void startPushRelabel() { void startPush() { // Paramters for heuristics const int BF_HEURISTIC_EPSILON_BOUND = 1000;
Note: See TracChangeset for help on using the changeset viewer.