[1956] | 1 | /* -*- C++ -*- |
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| 2 | * |
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| 3 | * This file is a part of LEMON, a generic C++ optimization library |
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| 4 | * |
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| 5 | * Copyright (C) 2003-2006 |
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| 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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| 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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| 8 | * |
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| 9 | * Permission to use, modify and distribute this software is granted |
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| 10 | * provided that this copyright notice appears in all copies. For |
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| 11 | * precise terms see the accompanying LICENSE file. |
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| 12 | * |
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| 13 | * This software is provided "AS IS" with no warranty of any kind, |
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| 14 | * express or implied, and with no claim as to its suitability for any |
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| 15 | * purpose. |
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| 16 | * |
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| 17 | */ |
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| 18 | |
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[1633] | 19 | #ifndef LEMON_SIMANN_H |
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| 20 | #define LEMON_SIMANN_H |
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| 21 | |
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| 22 | /// \ingroup experimental |
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| 23 | /// \file |
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| 24 | /// \brief Simulated annealing framework. |
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[1847] | 25 | /// |
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| 26 | /// \todo A test and some demo should be added |
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| 27 | /// \todo Doc should be improved |
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[1633] | 28 | /// \author Akos Ladanyi |
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| 29 | |
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| 30 | #include <cstdlib> |
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| 31 | #include <cmath> |
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[1918] | 32 | #include <limits> |
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[1633] | 33 | #include <lemon/time_measure.h> |
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| 34 | |
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| 35 | namespace lemon { |
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| 36 | |
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| 37 | /// \addtogroup experimental |
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| 38 | /// @{ |
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| 39 | |
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[1932] | 40 | class SimAnnBase; |
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| 41 | |
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[1918] | 42 | /// \brief A base class for controllers. |
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[1633] | 43 | class ControllerBase { |
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[1918] | 44 | public: |
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[1633] | 45 | friend class SimAnnBase; |
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[1918] | 46 | /// \brief Pointer to the simulated annealing base class. |
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[1633] | 47 | SimAnnBase *simann; |
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[1918] | 48 | /// \brief Initializes the controller. |
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[1633] | 49 | virtual void init() {} |
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[1918] | 50 | /// \brief This is called by the simulated annealing class when a |
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| 51 | /// neighbouring state gets accepted. |
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[1633] | 52 | virtual void acceptEvent() {} |
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[1918] | 53 | /// \brief This is called by the simulated annealing class when the |
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| 54 | /// accepted neighbouring state's cost is less than the best found one's. |
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[1633] | 55 | virtual void improveEvent() {} |
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[1918] | 56 | /// \brief This is called by the simulated annealing class when a |
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| 57 | /// neighbouring state gets rejected. |
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[1633] | 58 | virtual void rejectEvent() {} |
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[1918] | 59 | /// \brief Decides whether to continue the annealing process or not. |
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[1633] | 60 | virtual bool next() = 0; |
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[1918] | 61 | /// \brief Decides whether to accept the current solution or not. |
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[1633] | 62 | virtual bool accept() = 0; |
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[1918] | 63 | /// \brief Destructor. |
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| 64 | virtual ~ControllerBase() {} |
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[1633] | 65 | }; |
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| 66 | |
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[1918] | 67 | /// \brief Skeleton of an entity class. |
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[1633] | 68 | class EntityBase { |
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| 69 | public: |
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[1918] | 70 | /// \brief Makes a minor change to the entity. |
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| 71 | /// \return the new cost |
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[1633] | 72 | virtual double mutate() = 0; |
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[1918] | 73 | /// \brief Restores the entity to its previous state i.e. reverts the |
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| 74 | /// effects of the last mutate(). |
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[1633] | 75 | virtual void revert() = 0; |
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[1918] | 76 | /// \brief Makes a copy of the entity. |
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[1633] | 77 | virtual EntityBase* clone() = 0; |
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[1918] | 78 | /// \brief Makes a major change to the entity. |
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[1633] | 79 | virtual void randomize() = 0; |
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[1918] | 80 | /// \brief Destructor. |
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| 81 | virtual ~EntityBase() {} |
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[1633] | 82 | }; |
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| 83 | |
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[1918] | 84 | /// \brief Simulated annealing abstract base class. |
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| 85 | /// Can be used to derive a custom simulated annealing class if \ref SimAnn |
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| 86 | /// doesn't fit your needs. |
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[1633] | 87 | class SimAnnBase { |
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| 88 | private: |
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[1918] | 89 | /// \brief Pointer to the controller. |
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[1633] | 90 | ControllerBase *controller; |
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[1918] | 91 | /// \brief Cost of the current solution. |
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[1633] | 92 | double curr_cost; |
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[1918] | 93 | /// \brief Cost of the best solution. |
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[1633] | 94 | double best_cost; |
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[1918] | 95 | /// \brief Cost of the previous solution. |
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[1633] | 96 | double prev_cost; |
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[1918] | 97 | /// \brief Cost of the solution preceding the previous one. |
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[1633] | 98 | double prev_prev_cost; |
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[1918] | 99 | /// \brief Number of iterations. |
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[1633] | 100 | long iter; |
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[1918] | 101 | /// \brief Number of iterations which did not improve the solution since |
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| 102 | /// the last improvement. |
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[1633] | 103 | long last_impr; |
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| 104 | protected: |
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[1918] | 105 | /// \brief Step to a neighbouring state. |
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[1633] | 106 | virtual double mutate() = 0; |
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[1918] | 107 | /// \brief Reverts the last mutate(). |
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[1633] | 108 | virtual void revert() = 0; |
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[1918] | 109 | /// \brief Saves the current solution as the best one. |
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[1633] | 110 | virtual void saveAsBest() = 0; |
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[1918] | 111 | /// \brief Does initializations before each run. |
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[1633] | 112 | virtual void init() { |
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| 113 | controller->init(); |
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| 114 | curr_cost = prev_cost = prev_prev_cost = best_cost = |
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| 115 | std::numeric_limits<double>::infinity(); |
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| 116 | iter = last_impr = 0; |
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| 117 | } |
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| 118 | public: |
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[1918] | 119 | /// \brief Sets the controller class to use. |
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[1633] | 120 | void setController(ControllerBase &_controller) { |
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| 121 | controller = &_controller; |
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| 122 | controller->simann = this; |
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| 123 | } |
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[1918] | 124 | /// \brief Returns the cost of the current solution. |
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[1633] | 125 | double getCurrCost() const { return curr_cost; } |
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[1918] | 126 | /// \brief Returns the cost of the previous solution. |
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[1633] | 127 | double getPrevCost() const { return prev_cost; } |
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[1918] | 128 | /// \brief Returns the cost of the best solution. |
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[1633] | 129 | double getBestCost() const { return best_cost; } |
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[1918] | 130 | /// \brief Returns the number of iterations done. |
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[1633] | 131 | long getIter() const { return iter; } |
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[1918] | 132 | /// \brief Returns the ordinal number of the last iteration when the |
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| 133 | /// solution was improved. |
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[1633] | 134 | long getLastImpr() const { return last_impr; } |
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[1918] | 135 | /// \brief Performs one iteration. |
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[1633] | 136 | bool step() { |
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| 137 | iter++; |
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| 138 | prev_prev_cost = prev_cost; |
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| 139 | prev_cost = curr_cost; |
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| 140 | curr_cost = mutate(); |
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| 141 | if (controller->accept()) { |
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| 142 | controller->acceptEvent(); |
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| 143 | last_impr = iter; |
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| 144 | if (curr_cost < best_cost) { |
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| 145 | best_cost = curr_cost; |
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| 146 | saveAsBest(); |
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| 147 | controller->improveEvent(); |
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| 148 | } |
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| 149 | } |
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| 150 | else { |
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| 151 | revert(); |
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| 152 | curr_cost = prev_cost; |
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| 153 | prev_cost = prev_prev_cost; |
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| 154 | controller->rejectEvent(); |
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| 155 | } |
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| 156 | return controller->next(); |
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| 157 | } |
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[1918] | 158 | /// \brief Performs a given number of iterations. |
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| 159 | /// \param n the number of iterations |
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[1633] | 160 | bool step(int n) { |
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| 161 | for(; n > 0 && step(); --n) ; |
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| 162 | return !n; |
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| 163 | } |
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[1918] | 164 | /// \brief Starts the annealing process. |
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[1633] | 165 | void run() { |
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| 166 | init(); |
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| 167 | do { } while (step()); |
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| 168 | } |
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[1918] | 169 | /// \brief Destructor. |
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| 170 | virtual ~SimAnnBase() {} |
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[1633] | 171 | }; |
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| 172 | |
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[1918] | 173 | /// \brief Simulated annealing class. |
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[1633] | 174 | class SimAnn : public SimAnnBase { |
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| 175 | private: |
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[1918] | 176 | /// \brief Pointer to the current entity. |
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[1633] | 177 | EntityBase *curr_ent; |
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[1918] | 178 | /// \brief Pointer to the best entity. |
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[1633] | 179 | EntityBase *best_ent; |
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[1918] | 180 | /// \brief Does initializations before each run. |
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[1633] | 181 | void init() { |
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| 182 | SimAnnBase::init(); |
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| 183 | if (best_ent) delete best_ent; |
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| 184 | best_ent = NULL; |
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| 185 | curr_ent->randomize(); |
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| 186 | } |
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| 187 | public: |
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[1918] | 188 | /// \brief Constructor. |
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[1633] | 189 | SimAnn() : curr_ent(NULL), best_ent(NULL) {} |
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[1918] | 190 | /// \brief Destructor. |
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[1633] | 191 | virtual ~SimAnn() { |
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| 192 | if (best_ent) delete best_ent; |
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| 193 | } |
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[1918] | 194 | /// \brief Step to a neighbouring state. |
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[1633] | 195 | double mutate() { |
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| 196 | return curr_ent->mutate(); |
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| 197 | } |
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[1918] | 198 | /// \brief Reverts the last mutate(). |
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[1633] | 199 | void revert() { |
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| 200 | curr_ent->revert(); |
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| 201 | } |
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[1918] | 202 | /// \brief Saves the current solution as the best one. |
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[1633] | 203 | void saveAsBest() { |
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| 204 | if (best_ent) delete best_ent; |
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| 205 | best_ent = curr_ent->clone(); |
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| 206 | } |
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[1918] | 207 | /// \brief Sets the current entity. |
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[1633] | 208 | void setEntity(EntityBase &_ent) { |
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| 209 | curr_ent = &_ent; |
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| 210 | } |
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[1918] | 211 | /// \brief Returns a copy of the best found entity. |
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[1633] | 212 | EntityBase* getBestEntity() { return best_ent->clone(); } |
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| 213 | }; |
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| 214 | |
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[1918] | 215 | /// \brief A simple controller for the simulated annealing class. |
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| 216 | /// This controller starts from a given initial temperature and evenly |
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| 217 | /// decreases it. |
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[1633] | 218 | class SimpleController : public ControllerBase { |
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[1918] | 219 | private: |
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| 220 | /// \brief Maximum number of iterations. |
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| 221 | long max_iter; |
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| 222 | /// \brief Maximum number of iterations which do not improve the |
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| 223 | /// solution. |
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| 224 | long max_no_impr; |
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| 225 | /// \brief Temperature. |
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| 226 | double temp; |
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| 227 | /// \brief Annealing factor. |
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| 228 | double ann_fact; |
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| 229 | /// \brief Constructor. |
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| 230 | /// \param _max_iter maximum number of iterations |
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| 231 | /// \param _max_no_impr maximum number of consecutive iterations which do |
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| 232 | /// not yield a better solution |
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| 233 | /// \param _temp initial temperature |
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| 234 | /// \param _ann_fact annealing factor |
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[1633] | 235 | public: |
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| 236 | SimpleController(long _max_iter = 500000, long _max_no_impr = 20000, |
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| 237 | double _temp = 1000.0, double _ann_fact = 0.9999) : max_iter(_max_iter), |
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| 238 | max_no_impr(_max_no_impr), temp(_temp), ann_fact(_ann_fact) |
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| 239 | { |
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| 240 | srand48(time(0)); |
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| 241 | } |
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[1918] | 242 | /// \brief This is called when a neighbouring state gets accepted. |
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[1633] | 243 | void acceptEvent() {} |
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[1918] | 244 | /// \brief This is called when the accepted neighbouring state's cost is |
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| 245 | /// less than the best found one's. |
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[1633] | 246 | void improveEvent() {} |
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[1918] | 247 | /// \brief This is called when a neighbouring state gets rejected. |
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[1633] | 248 | void rejectEvent() {} |
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[1918] | 249 | /// \brief Decides whether to continue the annealing process or not. Also |
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| 250 | /// decreases the temperature. |
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[1633] | 251 | bool next() { |
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| 252 | temp *= ann_fact; |
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| 253 | bool quit = (simann->getIter() > max_iter) || |
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| 254 | (simann->getIter() - simann->getLastImpr() > max_no_impr); |
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| 255 | return !quit; |
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| 256 | } |
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[1918] | 257 | /// \brief Decides whether to accept the current solution or not. |
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[1633] | 258 | bool accept() { |
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[1918] | 259 | double cost_diff = simann->getCurrCost() - simann->getPrevCost(); |
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| 260 | return (drand48() <= exp(-(cost_diff / temp))); |
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[1633] | 261 | } |
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[1918] | 262 | /// \brief Destructor. |
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| 263 | virtual ~SimpleController() {} |
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[1633] | 264 | }; |
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| 265 | |
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[1918] | 266 | /// \brief A controller with preset running time for the simulated annealing |
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| 267 | /// class. |
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| 268 | /// With this controller you can set the running time of the annealing |
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| 269 | /// process in advance. It works the following way: the controller measures |
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| 270 | /// a kind of divergence. The divergence is the difference of the average |
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| 271 | /// cost of the recently found solutions the cost of the best found one. In |
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| 272 | /// case this divergence is greater than a given threshold, then we decrease |
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| 273 | /// the annealing factor, that is we cool the system faster. In case the |
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| 274 | /// divergence is lower than the threshold, then we increase the temperature. |
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| 275 | /// The threshold is a function of the elapsed time which reaches zero at the |
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| 276 | /// desired end time. |
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[1633] | 277 | class AdvancedController : public ControllerBase { |
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| 278 | private: |
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[1918] | 279 | /// \brief Timer class to measure the elapsed time. |
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[1633] | 280 | Timer timer; |
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[1918] | 281 | /// \brief Calculates the threshold value. |
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| 282 | /// \param time the elapsed time in seconds |
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[1633] | 283 | virtual double threshold(double time) { |
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| 284 | return (-1.0) * start_threshold / end_time * time + start_threshold; |
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| 285 | } |
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[1918] | 286 | /// \brief Parameter used to calculate the running average. |
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| 287 | double alpha; |
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| 288 | /// \brief Parameter used to decrease the annealing factor. |
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| 289 | double beta; |
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| 290 | /// \brief Parameter used to increase the temperature. |
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| 291 | double gamma; |
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| 292 | /// \brief The time at the end of the algorithm. |
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| 293 | double end_time; |
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| 294 | /// \brief The time at the start of the algorithm. |
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| 295 | double start_time; |
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| 296 | /// \brief Starting threshold. |
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| 297 | double start_threshold; |
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| 298 | /// \brief Average cost of recent solutions. |
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| 299 | double avg_cost; |
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| 300 | /// \brief Temperature. |
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| 301 | double temp; |
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| 302 | /// \brief Annealing factor. |
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| 303 | double ann_fact; |
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| 304 | /// \brief Initial annealing factor. |
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| 305 | double init_ann_fact; |
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| 306 | /// \brief True when the annealing process has been started. |
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| 307 | bool start; |
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[1633] | 308 | public: |
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[1918] | 309 | /// \brief Constructor. |
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| 310 | /// \param _end_time running time in seconds |
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| 311 | /// \param _alpha parameter used to calculate the running average |
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| 312 | /// \param _beta parameter used to decrease the annealing factor |
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| 313 | /// \param _gamma parameter used to increase the temperature |
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| 314 | /// \param _ann_fact initial annealing factor |
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[1633] | 315 | AdvancedController(double _end_time, double _alpha = 0.2, |
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| 316 | double _beta = 0.9, double _gamma = 1.6, double _ann_fact = 0.9999) : |
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| 317 | alpha(_alpha), beta(_beta), gamma(_gamma), end_time(_end_time), |
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[1918] | 318 | ann_fact(_ann_fact), init_ann_fact(_ann_fact), start(false) |
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[1633] | 319 | { |
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| 320 | srand48(time(0)); |
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| 321 | } |
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[1918] | 322 | /// \brief Does initializations before each run. |
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[1633] | 323 | void init() { |
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| 324 | avg_cost = simann->getCurrCost(); |
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| 325 | } |
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[1918] | 326 | /// \brief This is called when a neighbouring state gets accepted. |
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[1633] | 327 | void acceptEvent() { |
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| 328 | avg_cost = alpha * simann->getCurrCost() + (1.0 - alpha) * avg_cost; |
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[1918] | 329 | if (!start) { |
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[1633] | 330 | static int cnt = 0; |
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| 331 | cnt++; |
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| 332 | if (cnt >= 100) { |
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| 333 | // calculate starting threshold and starting temperature |
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| 334 | start_threshold = 5.0 * fabs(simann->getBestCost() - avg_cost); |
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| 335 | temp = 10000.0; |
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[1918] | 336 | start = true; |
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[1847] | 337 | timer.restart(); |
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[1633] | 338 | } |
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| 339 | } |
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| 340 | } |
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[1918] | 341 | /// \brief Decides whether to continue the annealing process or not. |
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[1633] | 342 | bool next() { |
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[1918] | 343 | if (!start) { |
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[1633] | 344 | return true; |
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| 345 | } |
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| 346 | else { |
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[1918] | 347 | double elapsed_time = timer.realTime(); |
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[1633] | 348 | if (fabs(avg_cost - simann->getBestCost()) > threshold(elapsed_time)) { |
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| 349 | // decrease the annealing factor |
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| 350 | ann_fact *= beta; |
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| 351 | } |
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| 352 | else { |
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| 353 | // increase the temperature |
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| 354 | temp *= gamma; |
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| 355 | // reset the annealing factor |
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| 356 | ann_fact = init_ann_fact; |
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| 357 | } |
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| 358 | temp *= ann_fact; |
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| 359 | return elapsed_time < end_time; |
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| 360 | } |
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| 361 | } |
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[1918] | 362 | /// \brief Decides whether to accept the current solution or not. |
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[1633] | 363 | bool accept() { |
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[1918] | 364 | if (!start) { |
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[1633] | 365 | return true; |
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| 366 | } |
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| 367 | else { |
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[1918] | 368 | double cost_diff = simann->getCurrCost() - simann->getPrevCost(); |
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| 369 | return (drand48() <= exp(-(cost_diff / temp))); |
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[1633] | 370 | } |
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| 371 | } |
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[1918] | 372 | /// \brief Destructor. |
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| 373 | virtual ~AdvancedController() {} |
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[1633] | 374 | }; |
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| 375 | |
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| 376 | /// @} |
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| 377 | |
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| 378 | } |
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| 379 | |
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| 380 | #endif |
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