001 package net.sf.cpsolver.ifs.perturbations;
002
003 import java.util.Collection;
004 import java.util.Map;
005
006 import net.sf.cpsolver.ifs.model.Model;
007 import net.sf.cpsolver.ifs.model.Value;
008 import net.sf.cpsolver.ifs.model.Variable;
009 import net.sf.cpsolver.ifs.solution.Solution;
010 import net.sf.cpsolver.ifs.solver.Solver;
011
012 /**
013 * Counter of perturbation penalty (minimal perturbation problem). <br>
014 * <br>
015 * Many real-life problems are dynamic, with changes in the problem definition
016 * occurring after a solution to the initial formulation has been reached. A
017 * minimal perturbation problem incorporates these changes, along with the
018 * initial solution, as a new problem whose solution must be as close as
019 * possible to the initial solution. The iterative forward search algorithm is
020 * also made to solve minimal perturbation problems. <br>
021 * <br>
022 * To define the minimal perturbation problem, we will consider an initial
023 * (original) problem, its solution, a new problem, and some distance function
024 * which allows us to compare solutions of the initial and the new problem.
025 * Subsequently we look for a solution of the new problem with minimal distance
026 * from the initial solution. This distance is expressed by this
027 * PerturbationCounter
028 *
029 * @see Solver
030 * @see Solution
031 * @see Variable
032 *
033 * @version IFS 1.2 (Iterative Forward Search)<br>
034 * Copyright (C) 2006 - 2010 Tomas Muller<br>
035 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
036 * <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
037 * <br>
038 * This library is free software; you can redistribute it and/or modify
039 * it under the terms of the GNU Lesser General Public License as
040 * published by the Free Software Foundation; either version 3 of the
041 * License, or (at your option) any later version. <br>
042 * <br>
043 * This library is distributed in the hope that it will be useful, but
044 * WITHOUT ANY WARRANTY; without even the implied warranty of
045 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
046 * Lesser General Public License for more details. <br>
047 * <br>
048 * You should have received a copy of the GNU Lesser General Public
049 * License along with this library; if not see
050 * <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
051 */
052 public interface PerturbationsCounter<V extends Variable<V, T>, T extends Value<V, T>> {
053 /** Initialization */
054 public void init(Solver<V, T> solver);
055
056 /**
057 * Returns perturbation penalty, i.e., the distance between current solution
058 * and the solution of the initial problem (see
059 * {@link Variable#getInitialAssignment()}).
060 *
061 * @param model
062 * current model
063 */
064 public double getPerturbationPenalty(Model<V, T> model);
065
066 /**
067 * Returns perturbation penalty, i.e., the distance between current solution
068 * and the solution of the initial (only include variables from the given
069 * set) problem (see {@link Variable#getInitialAssignment()}).
070 *
071 * @param model
072 * current model
073 */
074 public double getPerturbationPenalty(Model<V, T> model, Collection<V> variables);
075
076 /**
077 * Returns perturbation penalty of the solution which become from the
078 * current solution when given conflicting values are unassigned and the
079 * selected value is assigned. Since this penalty is used for comparison of
080 * different candidate values in the value selection criterion, it is fully
081 * acceptable to just return a difference between current and the altered
082 * solution (which might be easied for computation that the whole
083 * perturbation penalty).
084 *
085 * @param model
086 * current model
087 * @param selectedValue
088 * value to be selected in the next iteration
089 * @param conflicts
090 * conflicting values to be unassigned in the next iteration
091 */
092 public double getPerturbationPenalty(Model<V, T> model, T selectedValue, Collection<T> conflicts);
093
094 /**
095 * Some (perturbation) information about the solution might be returned
096 * here.
097 *
098 * @param info
099 * resultant info table
100 * @param model
101 * current model
102 */
103 public void getInfo(Map<String, String> info, Model<V, T> model);
104
105 /**
106 * Some (perturbation) information about the solution might be returned here
107 * (only include variables from the given set).
108 *
109 * @param info
110 * resultant info table
111 * @param model
112 * current model
113 */
114 public void getInfo(Map<String, String> info, Model<V, T> model, Collection<V> variables);
115 }