001package org.cpsolver.ifs.model; 002 003import java.util.HashMap; 004import java.util.Map; 005 006import org.cpsolver.ifs.assignment.Assignment; 007import org.cpsolver.ifs.model.Model; 008import org.cpsolver.ifs.model.Value; 009import org.cpsolver.ifs.model.Variable; 010 011 012/** 013 * Lazy swap of two variables. See {@link LazyNeighbour}. 014 * 015 * @version IFS 1.3 (Iterative Forward Search)<br> 016 * Copyright (C) 2013 - 2014 Tomas Muller<br> 017 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 018 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 019 * <br> 020 * This library is free software; you can redistribute it and/or 021 * modify it under the terms of the GNU Lesser General Public 022 * License as published by the Free Software Foundation; either 023 * version 3 of the License, or (at your option) any later version. 024 * <br><br> 025 * This library is distributed in the hope that it will be useful, 026 * but WITHOUT ANY WARRANTY; without even the implied warranty of 027 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 028 * Lesser General Public License for more details. 029 * <br><br> 030 * You should have received a copy of the GNU Lesser General Public 031 * License along with this library; if not see 032 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>. 033 * 034 * @param <V> Variable 035 * @param <T> Value 036 */ 037public class LazySwap<V extends Variable<V, T>, T extends Value<V, T>> extends LazyNeighbour<V, T> { 038 private T iV1, iV2, iOldV1 = null, iOldV2 = null; 039 040 /** 041 * Constructor 042 * @param v1 first variable 043 * @param v2 second variable 044 */ 045 public LazySwap(T v1, T v2) { 046 iV1 = v1; 047 iV2 = v2; 048 } 049 050 /** Perform swap */ 051 @Override 052 protected void doAssign(Assignment<V, T> assignment, long iteration) { 053 iOldV1 = assignment.getValue(iV1.variable()); 054 iOldV2 = assignment.getValue(iV2.variable()); 055 if (iOldV1 != null) assignment.unassign(iteration, iV1.variable()); 056 if (iOldV2 != null) assignment.unassign(iteration, iV2.variable()); 057 assignment.assign(iteration, iV1); 058 assignment.assign(iteration, iV2); 059 } 060 061 /** Undo the swap */ 062 @Override 063 protected void undoAssign(Assignment<V, T> assignment, long iteration) { 064 assignment.unassign(iteration, iV1.variable()); 065 assignment.unassign(iteration, iV2.variable()); 066 if (iOldV1 != null) assignment.assign(iteration, iOldV1); 067 if (iOldV2 != null) assignment.assign(iteration, iOldV2); 068 } 069 /** Return problem model */ 070 @Override 071 public Model<V,T> getModel() { 072 return iV1.variable().getModel(); 073 } 074 075 /** String representation */ 076 @Override 077 public String toString() { 078 return "Lazy "+iOldV1+" -> "+iV1+", "+iOldV2+" -> "+iV2; 079 } 080 081 @Override 082 public Map<V, T> assignments() { 083 Map<V, T> ret = new HashMap<V, T>(); 084 ret.put(iV1.variable(), iV1); 085 ret.put(iV2.variable(), iV2); 086 return ret; 087 } 088 089}