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.ifs.util.Progress; 009import org.cpsolver.studentsct.model.Enrollment; 010import org.cpsolver.studentsct.model.Request; 011 012/** 013 * A simple step that checks whether the best solution has improved since the last check. 014 * If there is no improvement, restore the best solution (reset the search to start from the best 015 * solution again). The checking is done in the seletion's initialization phase, 016 * no neighbors are actually computed. 017 * 018 * @version StudentSct 1.3 (Student Sectioning)<br> 019 * Copyright (C) 2007 - 2014 Tomáš Müller<br> 020 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 021 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 022 * <br> 023 * This library is free software; you can redistribute it and/or modify 024 * it under the terms of the GNU Lesser General Public License as 025 * published by the Free Software Foundation; either version 3 of the 026 * License, or (at your option) any later version. <br> 027 * <br> 028 * This library is distributed in the hope that it will be useful, but 029 * WITHOUT ANY WARRANTY; without even the implied warranty of 030 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 031 * Lesser General Public License for more details. <br> 032 * <br> 033 * You should have received a copy of the GNU Lesser General Public 034 * License along with this library; if not see 035 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 036 */ 037public class RestoreBestSolution implements NeighbourSelection<Request, Enrollment> { 038 private Double iBestValue = null; 039 040 public RestoreBestSolution(DataProperties config) { 041 } 042 043 @Override 044 public void init(Solver<Request, Enrollment> solver) { 045 Progress.getInstance(solver.currentSolution().getModel()).setPhase("Restore best...", 1); 046 if (solver.currentSolution().getBestInfo() == null) return; // no best saved yet 047 if (iBestValue == null || iBestValue > solver.currentSolution().getBestValue()) { 048 Progress.getInstance(solver.currentSolution().getModel()).debug("best value marked"); 049 iBestValue = solver.currentSolution().getBestValue(); 050 } else { 051 Progress.getInstance(solver.currentSolution().getModel()).debug("best solution restored"); 052 solver.currentSolution().restoreBest(); 053 } 054 } 055 056 057 @Override 058 public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) { 059 return null; 060 } 061 062}