    001package org.cpsolver.ifs.perturbations;
    002
    003import java.util.Collection;
    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;
    010import org.cpsolver.ifs.solution.Solution;
    011import org.cpsolver.ifs.solver.Solver;
    012
    013
    014/**
    015 * Counter of perturbation penalty (minimal perturbation problem). <br>
    016 * <br>
    017 * Many real-life problems are dynamic, with changes in the problem definition
    018 * occurring after a solution to the initial formulation has been reached. A
    019 * minimal perturbation problem incorporates these changes, along with the
    020 * initial solution, as a new problem whose solution must be as close as
    021 * possible to the initial solution. The iterative forward search algorithm is
    022 * also made to solve minimal perturbation problems. <br>
    023 * <br>
    024 * To define the minimal perturbation problem, we will consider an initial
    025 * (original) problem, its solution, a new problem, and some distance function
    026 * which allows us to compare solutions of the initial and the new problem.
    027 * Subsequently we look for a solution of the new problem with minimal distance
    028 * from the initial solution. This distance is expressed by this
    029 * PerturbationCounter
    030 *
    031 * @see Solver
    032 * @see Solution
    033 * @see Variable
    034 *
    035 * @author  Tomáš Müller
    036 * @version IFS 1.3 (Iterative Forward Search)<br>
    037 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    038 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    039 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    040 * <br>
    041 *          This library is free software; you can redistribute it and/or modify
    042 *          it under the terms of the GNU Lesser General Public License as
    043 *          published by the Free Software Foundation; either version 3 of the
    044 *          License, or (at your option) any later version. <br>
    045 * <br>
    046 *          This library is distributed in the hope that it will be useful, but
    047 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    048 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    049 *          Lesser General Public License for more details. <br>
    050 * <br>
    051 *          You should have received a copy of the GNU Lesser General Public
    052 *          License along with this library; if not see
    053 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    054 *
    055 * @param <V> Variable
    056 * @param <T> Value
    057 */
    058public interface PerturbationsCounter<V extends Variable<V, T>, T extends Value<V, T>> {
    059    /** Initialization
    060     * @param solver current solver
    061     **/
    062    public void init(Solver<V, T> solver);
    063
    064    /**
    065     * Returns perturbation penalty, i.e., the distance between current solution
    066     * and the solution of the initial problem (see
    067     * {@link Variable#getInitialAssignment()}).
    068     *
    069     * @param assignment current assignment
    070     * @param model
    071     *            current model
    072     * @return penalty
    073     */
    074    public double getPerturbationPenalty(Assignment<V, T> assignment, Model<V, T> model);
    075
    076    /**
    077     * Returns perturbation penalty, i.e., the distance between current solution
    078     * and the solution of the initial (only include variables from the given
    079     * set) problem (see {@link Variable#getInitialAssignment()}).
    080     *
    081     * @param assignment current assignment
    082     * @param model
    083     *            current model
    084     * @param variables sub-problem
    085     * @return penalty
    086     */
    087    public double getPerturbationPenalty(Assignment<V, T> assignment, Model<V, T> model, Collection<V> variables);
    088
    089    /**
    090     * Returns perturbation penalty of the solution which become from the
    091     * current solution when given conflicting values are unassigned and the
    092     * selected value is assigned. Since this penalty is used for comparison of
    093     * different candidate values in the value selection criterion, it is fully
    094     * acceptable to just return a difference between current and the altered
    095     * solution (which might be easied for computation that the whole
    096     * perturbation penalty).
    097     *
    098     * @param assignment current assignment
    099     * @param model
    100     *            current model
    101     * @param selectedValue
    102     *            value to be selected in the next iteration
    103     * @param conflicts
    104     *            conflicting values to be unassigned in the next iteration
    105     * @return penalty
    106     */
    107    public double getPerturbationPenalty(Assignment<V, T> assignment, Model<V, T> model, T selectedValue, Collection<T> conflicts);
    108
    109    /**
    110     * Some (perturbation) information about the solution might be returned
    111     * here.
    112     *
    113     * @param assignment current assignment
    114     * @param info
    115     *            resultant info table
    116     * @param model
    117     *            current model
    118     */
    119    public void getInfo(Assignment<V, T> assignment, Model<V, T> model, Map<String, String> info);
    120
    121    /**
    122     * Some (perturbation) information about the solution might be returned here
    123     * (only include variables from the given set).
    124     *
    125     * @param assignment current assignment
    126     * @param info
    127     *            resultant info table
    128     * @param model
    129     *            current model
    130     * @param variables sub-problem
    131     */
    132    public void getInfo(Assignment<V, T> assignment, Model<V, T> model, Map<String, String> info, Collection<V> variables);
    133}