001package net.sf.cpsolver.ifs.constant; 002 003 004import java.util.ArrayList; 005import java.util.List; 006 007import net.sf.cpsolver.ifs.model.Model; 008import net.sf.cpsolver.ifs.model.Value; 009import net.sf.cpsolver.ifs.model.Variable; 010 011/** 012 * Extension of the model with constant variables. 013 * 014 * Such variables are excluded from the solver process, however, they can be 015 * included in constraints. Such model can allow us to build a solution on top 016 * of another solution (e.g., committed classes in the course timetabling). 017 * 018 * Constant variable has to implement interface {@link ConstantVariable}, 019 * returning {@link ConstantVariable#isConstant()} true. 020 * 021 * @version IFS 1.2 (Iterative Forward Search)<br> 022 * Copyright (C) 2006 - 2010 Tomáš Müller<br> 023 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br> 024 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br> 025 * <br> 026 * This library is free software; you can redistribute it and/or modify 027 * it under the terms of the GNU Lesser General Public License as 028 * published by the Free Software Foundation; either version 3 of the 029 * License, or (at your option) any later version. <br> 030 * <br> 031 * This library is distributed in the hope that it will be useful, but 032 * WITHOUT ANY WARRANTY; without even the implied warranty of 033 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 034 * Lesser General Public License for more details. <br> 035 * <br> 036 * You should have received a copy of the GNU Lesser General Public 037 * License along with this library; if not see <http://www.gnu.org/licenses/>. 038 * 039 */ 040 041public class ConstantModel<V extends Variable<V, T>, T extends Value<V, T>> extends Model<V, T> { 042 private List<V> iConstantVariables = null; 043 044 /** List of constant variables */ 045 public List<V> constantVariables() { 046 return iConstantVariables; 047 } 048 049 /** True, if the model contains at least one constant variable. */ 050 public boolean hasConstantVariables() { 051 return iConstantVariables != null && !iConstantVariables.isEmpty(); 052 } 053 054 /** True, if the given variable is constant. */ 055 public boolean isConstant(V variable) { 056 return (iConstantVariables != null && variable instanceof ConstantVariable && ((ConstantVariable) variable) 057 .isConstant()); 058 } 059 060 /** Adds a variable to the model */ 061 @Override 062 public void addVariable(V variable) { 063 if (variable instanceof ConstantVariable && ((ConstantVariable) variable).isConstant()) { 064 if (iConstantVariables == null) 065 iConstantVariables = new ArrayList<V>(); 066 variable.setModel(this); 067 iConstantVariables.add(variable); 068 if (variable.getAssignment() != null) 069 variable.assign(0L, variable.getAssignment()); 070 } else 071 super.addVariable(variable); 072 } 073 074 /** Removes a variable from the model */ 075 @Override 076 public void removeVariable(V variable) { 077 if (isConstant(variable)) { 078 variable.setModel(null); 079 iConstantVariables.remove(variable); 080 } else 081 super.removeVariable(variable); 082 } 083 084 /** 085 * Called before a value is assigned to its variable. Constant variables are 086 * excluded from (re)assignment. 087 */ 088 @Override 089 public void beforeAssigned(long iteration, T value) { 090 if (!isConstant(value.variable())) 091 super.beforeAssigned(iteration, value); 092 } 093 094 /** 095 * Called before a value is unassigned from its variable. Constant variables 096 * are excluded from (re)assignment. 097 */ 098 @Override 099 public void beforeUnassigned(long iteration, T value) { 100 if (!isConstant(value.variable())) 101 super.beforeUnassigned(iteration, value); 102 } 103 104 /** 105 * Called after a value is assigned to its variable. Constant variables are 106 * excluded from (re)assignment. 107 */ 108 @Override 109 public void afterAssigned(long iteration, T value) { 110 if (!isConstant(value.variable())) 111 super.afterAssigned(iteration, value); 112 } 113 114 /** 115 * Called after a value is unassigned from its variable. Constant variables 116 * are excluded from (re)assignment. 117 */ 118 @Override 119 public void afterUnassigned(long iteration, T value) { 120 if (!isConstant(value.variable())) 121 super.afterUnassigned(iteration, value); 122 } 123}