001package net.sf.cpsolver.ifs.solution; 002 003import net.sf.cpsolver.ifs.model.Value; 004import net.sf.cpsolver.ifs.model.Variable; 005import net.sf.cpsolver.ifs.util.DataProperties; 006 007/** 008 * General implementation of solution comparator for minimal perturbation 009 * problem. <br> 010 * <br> 011 * The solution is better than the best ever found solution when it has more 012 * variables assigned. In the case, when both solutions have the same number of 013 * assigned variables, the one with smaller number of perturbations (i.e., 014 * variables assigned to non-initial values) is selected. When all solution have 015 * the same number of assigned variables and number of perturbations, better 016 * solution is the one with smaller total value, i.e., the sum of 017 * {@link net.sf.cpsolver.ifs.model.Value#toDouble()} over all assigned 018 * variables. 019 * 020 * @see Solution 021 * @see net.sf.cpsolver.ifs.solver.Solver 022 * 023 * @version IFS 1.2 (Iterative Forward Search)<br> 024 * Copyright (C) 2006 - 2010 Tomáš Müller<br> 025 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 026 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 027 * <br> 028 * This library is free software; you can redistribute it and/or modify 029 * it under the terms of the GNU Lesser General Public License as 030 * published by the Free Software Foundation; either version 3 of the 031 * License, or (at your option) any later version. <br> 032 * <br> 033 * This library is distributed in the hope that it will be useful, but 034 * WITHOUT ANY WARRANTY; without even the implied warranty of 035 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 036 * Lesser General Public License for more details. <br> 037 * <br> 038 * You should have received a copy of the GNU Lesser General Public 039 * License along with this library; if not see 040 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 041 */ 042public class MPPSolutionComparator<V extends Variable<V, T>, T extends Value<V, T>> implements SolutionComparator<V, T> { 043 044 public MPPSolutionComparator() { 045 } 046 047 /** No parameters are used so far. */ 048 public MPPSolutionComparator(DataProperties properties) { 049 } 050 051 @Override 052 public boolean isBetterThanBestSolution(Solution<V, T> currentSolution) { 053 if (currentSolution.getBestInfo() == null) 054 return true; 055 int unassigned = currentSolution.getModel().nrUnassignedVariables(); 056 if (currentSolution.getModel().getBestUnassignedVariables() != unassigned) 057 return currentSolution.getModel().getBestUnassignedVariables() > unassigned; 058 int pert = currentSolution.getModel().perturbVariables().size(); 059 if (currentSolution.getModel().getBestPerturbations() != pert) 060 return currentSolution.getModel().getBestPerturbations() > pert; 061 return currentSolution.getModel().getTotalValue() < currentSolution.getBestValue(); 062 } 063 064}