001package org.cpsolver.studentsct.heuristics; 002 003import org.cpsolver.ifs.heuristics.NeighbourSelection; 004import org.cpsolver.ifs.model.Neighbour; 005import org.cpsolver.ifs.solution.Solution; 006import org.cpsolver.ifs.solver.Solver; 007import org.cpsolver.ifs.util.DataProperties; 008import org.cpsolver.studentsct.model.Enrollment; 009import org.cpsolver.studentsct.model.Request; 010 011/** 012 * A simple step that checks whether the best solution has improved since the last check. 013 * If there is no improvement, restore the best solution (reset the search to start from the best 014 * solution again). The checking is done in the seletion's initialization phase, 015 * no neighbors are actually computed. 016 * 017 * @version StudentSct 1.3 (Student Sectioning)<br> 018 * Copyright (C) 2007 - 2014 Tomas Muller<br> 019 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 020 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 021 * <br> 022 * This library is free software; you can redistribute it and/or modify 023 * it under the terms of the GNU Lesser General Public License as 024 * published by the Free Software Foundation; either version 3 of the 025 * License, or (at your option) any later version. <br> 026 * <br> 027 * This library is distributed in the hope that it will be useful, but 028 * WITHOUT ANY WARRANTY; without even the implied warranty of 029 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 030 * Lesser General Public License for more details. <br> 031 * <br> 032 * You should have received a copy of the GNU Lesser General Public 033 * License along with this library; if not see 034 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 035 */ 036public class RestoreBestSolution implements NeighbourSelection<Request, Enrollment> { 037 private Double iBestValue = null; 038 039 public RestoreBestSolution(DataProperties config) { 040 } 041 042 @Override 043 public void init(Solver<Request, Enrollment> solver) { 044 if (solver.currentSolution().getBestInfo() == null) return; // no best saved yet 045 if (iBestValue == null || iBestValue >= solver.currentSolution().getBestValue()) { 046 iBestValue = solver.currentSolution().getBestValue(); 047 } else { 048 solver.currentSolution().restoreBest(); 049 } 050 } 051 052 053 @Override 054 public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) { 055 return null; 056 } 057 058}