147 lines
4.7 KiB
C++
147 lines
4.7 KiB
C++
// METS lib source file - local-search.hh -*- C++ -*-
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//
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/*
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* Software License Agreement (BSD License)
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*
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* Copyright (c) 2006-2012, Mirko Maischberger <mirko.maischberger@gmail.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#ifndef LOCAL_SEARCH_HH_
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#define LOCAL_SEARCH_HH_
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namespace mets {
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/// @defgroup local_search Local Search
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/// @{
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/// @brief Local search algorithm.
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///
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/// With customary phase alternation
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/// and move managers generated neighborhood this can be used to do
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/// also a Random Restart Local Search, a Greedy Search,
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/// an Iterated Local Search and a Variable Neighborhood Search.
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template<typename move_manager_type>
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class local_search : public mets::abstract_search<move_manager_type>
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{
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public:
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/// @brief Creates a local search instance
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///
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/// @param working The working solution (this will be modified
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/// during search)
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///
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/// @param best_so_far A different solution
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/// instance used to store the best solution found
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///
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/// @param moveman A problem specific implementation of the
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/// move_manager_type concept used to generate the neighborhood.
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///
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/// @param short_circuit Wether the search should stop on
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/// the first improving move or not.
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local_search(evaluable_solution& starting_point,
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solution_recorder& recorder,
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move_manager_type& moveman,
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gol_type epsilon = 1e-7,
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bool short_circuit = false);
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/// purposely not implemented (see Effective C++)
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local_search(const local_search&);
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local_search& operator=(const local_search&);
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/// @brief This method starts the local search process.
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///
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/// To have a real local search you should provide an
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/// move_manager_type than enumerates all feasible
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/// moves.
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///
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virtual void
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search();
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protected:
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bool short_circuit_m;
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gol_type epsilon_m;
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};
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/// @}
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}
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template<typename move_manager_t>
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mets::local_search<move_manager_t>::local_search(evaluable_solution& working,
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solution_recorder& recorder,
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move_manager_t& moveman,
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gol_type epsilon,
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bool short_circuit)
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: abstract_search<move_manager_t>(working, recorder, moveman),
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short_circuit_m(short_circuit), epsilon_m(epsilon)
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{
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using base_t = abstract_search<move_manager_t>;
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base_t::step_m = 0;
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}
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template<typename move_manager_t>
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void
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mets::local_search<move_manager_t>::search()
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{
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using base_t = abstract_search<move_manager_t>;
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typename move_manager_t::iterator best_movit;
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base_t::solution_recorder_m.accept(base_t::working_solution_m);
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gol_type best_cost =
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static_cast<mets::evaluable_solution&>(base_t::working_solution_m)
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.cost_function();
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do
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{
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base_t::moves_m.refresh(base_t::working_solution_m);
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best_movit = base_t::moves_m.end();
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for(typename move_manager_t::iterator movit = base_t::moves_m.begin();
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movit != base_t::moves_m.end(); ++movit)
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{
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// evaluate the cost after the move
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gol_type cost = (*movit)->evaluate(base_t::working_solution_m);
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if(cost < best_cost - epsilon_m)
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{
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best_cost = cost;
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best_movit = movit;
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if(short_circuit_m) break;
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}
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} // end for each move
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if(best_movit != base_t::moves_m.end())
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{
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(*best_movit)->apply(base_t::working_solution_m);
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base_t::solution_recorder_m.accept(base_t::working_solution_m);
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base_t::current_move_m = best_movit;
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this->notify();
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}
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} while(best_movit != base_t::moves_m.end());
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}
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#endif
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