// METSlib source file - termination-criteria.hh -*- C++ -*- /* * Software License Agreement (BSD License) * * Copyright (c) 2006-2012, Mirko Maischberger * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following * disclaimer in the documentation and/or other materials provided * with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * */ #ifndef METS_TERMINATION_CRITERIA_HH_ #define METS_TERMINATION_CRITERIA_HH_ namespace mets { /// @defgroup common Termination criteria /// @{ /// @brief Function object expressing a termination criteria /// /// The search loop ends when the termination criteria is met. class termination_criteria_chain { public: /// @brief Constructor. /// /// @param next Optional next criterium in the chain. explicit termination_criteria_chain(termination_criteria_chain* next = 0) : next_m(next) { } /// purposely not implemented (see Effective C++) termination_criteria_chain(const termination_criteria_chain&); termination_criteria_chain& operator=(const termination_criteria_chain&); /// @brief Virtual destructor. virtual ~termination_criteria_chain() { } /// @brief Alternate function that decides if we shoud terminate the /// search process /// /// (chain of responsibility) /// /// @param fs The current working solution. /// @return True if we shoud terminate virtual bool operator()(const feasible_solution& fs); /// @brief Reset the criterion to its initial state. /// /// (chain of responsibility) /// virtual void reset(); protected: termination_criteria_chain* next_m; }; /// @brief Termination criteria based on the number of iterations. /// /// This termination criteria terminates the tabu-search /// after a fixed number of itarations. class iteration_termination_criteria : public termination_criteria_chain { public: /// @brief Ctor. Max is the number of iterations to do. iteration_termination_criteria(int max) : termination_criteria_chain(), max_m(max), iterations_m(max) {} explicit iteration_termination_criteria (termination_criteria_chain* next, int max) : termination_criteria_chain(next), max_m(max), iterations_m(max) {} bool operator()(const feasible_solution& fs) { if (iterations_m <= 0) return true; --iterations_m; return termination_criteria_chain::operator()(fs); } void reset() { iterations_m = max_m; termination_criteria_chain::reset(); } protected: int max_m; int iterations_m; }; /// @brief Termination criteria based on the number /// of iterations without an improvement. /// /// This termination criteria terminates the tabu-search /// after "max" number of itarations without a single /// global improvement. class noimprove_termination_criteria : public termination_criteria_chain { public: noimprove_termination_criteria(int max, gol_type epsilon = 1e-7) : termination_criteria_chain(), best_cost_m(std::numeric_limits::max()), max_noimprove_m(max), iterations_left_m(max), total_iterations_m(0), resets_m(0), second_guess_m(0), epsilon_m(epsilon) {} noimprove_termination_criteria (termination_criteria_chain* next, int max, gol_type epsilon = 1e-7) : termination_criteria_chain(next), best_cost_m(std::numeric_limits::max()), max_noimprove_m(max), iterations_left_m(max), total_iterations_m(0), resets_m(0), second_guess_m(0), epsilon_m(epsilon) { } bool operator()(const feasible_solution& fs); void reset() { iterations_left_m = max_noimprove_m; second_guess_m = total_iterations_m = resets_m = 0; best_cost_m = std::numeric_limits::max(); termination_criteria_chain::reset(); } int second_guess() const { return second_guess_m; } int iteration() const { return total_iterations_m; } int resets() const { return resets_m; } protected: gol_type best_cost_m; int max_noimprove_m; int iterations_left_m; int total_iterations_m; int resets_m; int second_guess_m; gol_type epsilon_m; }; /// @brief Termination criteria based on cost value /// /// This termination criteria terminates the tabu-search /// when a certain threshold is reached class threshold_termination_criteria : public termination_criteria_chain { public: threshold_termination_criteria(gol_type level, gol_type epsilon = 1e-7) : termination_criteria_chain(), level_m(level), epsilon_m(epsilon) { } threshold_termination_criteria (termination_criteria_chain* next, gol_type level, gol_type epsilon = 1e-7) : termination_criteria_chain(next), level_m(level), epsilon_m(epsilon) { } bool operator()(const feasible_solution& fs) { mets::gol_type current_cost = dynamic_cast(fs).cost_function(); if(current_cost < level_m + epsilon_m) return true; return termination_criteria_chain::operator()(fs); } void reset() { termination_criteria_chain::reset(); } protected: gol_type level_m; gol_type epsilon_m; }; /// The mets::forever termination criterion will never terminate the /// search. /// /// This can be used in the mets::simulated_annealing to stop only /// when the temperature reaches 0 or in the mets::tabu_search if we /// want to stop for another reason (e.g. some components or /// observer raises an exception). /// /// The forever termination criterion cannot be chained. When /// chained behaviour is undetermined. class forever : public termination_criteria_chain { public: forever() : termination_criteria_chain() {} bool operator()(const feasible_solution& /*fs*/) { return false; } void reset() { termination_criteria_chain::reset(); } }; /// @} } //________________________________________________________________________ inline bool mets::termination_criteria_chain::operator()(const feasible_solution& fs) { if(next_m) return next_m->operator()(fs); else return false; } //________________________________________________________________________ inline void mets::termination_criteria_chain::reset() { if(next_m) next_m->reset(); } //________________________________________________________________________ inline bool mets::noimprove_termination_criteria::operator()(const feasible_solution& fs) { mets::gol_type current_cost = dynamic_cast(fs).cost_function(); if(current_cost < best_cost_m - epsilon_m) { best_cost_m = current_cost; second_guess_m = std::max(second_guess_m, (max_noimprove_m - iterations_left_m)); iterations_left_m = max_noimprove_m; resets_m++; } if(iterations_left_m <= 0) return true; total_iterations_m++; --iterations_left_m; return termination_criteria_chain::operator()(fs); } #endif