001    package net.sf.cpsolver.ifs.heuristics;
002    
003    import net.sf.cpsolver.ifs.model.Value;
004    import net.sf.cpsolver.ifs.model.Variable;
005    import net.sf.cpsolver.ifs.solution.Solution;
006    import net.sf.cpsolver.ifs.solver.Solver;
007    
008    /**
009     * Value selection criterion. <br>
010     * <br>
011     * After a variable is selected, we need to find a value to be assigned to the
012     * variable. This problem is usually called "value selection" in constraint
013     * programming. Typically, the most useful advice is to select the best-fit
014     * value. So, we are looking for a value which is the most preferred for the
015     * variable and which causes the least trouble as well. This means that we need
016     * to find a value with the minimal potential for future conflicts with other
017     * variables. For example, a value which violates the smallest number of soft
018     * constraints can be selected among those with the smallest number of hard
019     * conflicts. <br>
020     * <br>
021     * The task of this criterion is to select a value of the given variable which
022     * will be assigned to this variable.
023     * 
024     * @see Solver
025     * 
026     * @version IFS 1.2 (Iterative Forward Search)<br>
027     *          Copyright (C) 2006 - 2010 Tomas Muller<br>
028     *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
029     *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
030     * <br>
031     *          This library is free software; you can redistribute it and/or modify
032     *          it under the terms of the GNU Lesser General Public License as
033     *          published by the Free Software Foundation; either version 3 of the
034     *          License, or (at your option) any later version. <br>
035     * <br>
036     *          This library is distributed in the hope that it will be useful, but
037     *          WITHOUT ANY WARRANTY; without even the implied warranty of
038     *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
039     *          Lesser General Public License for more details. <br>
040     * <br>
041     *          You should have received a copy of the GNU Lesser General Public
042     *          License along with this library; if not see <http://www.gnu.org/licenses/>.
043     **/
044    public interface ValueSelection<V extends Variable<V, T>, T extends Value<V, T>> {
045        /** Initialization */
046        public void init(Solver<V, T> solver);
047    
048        /**
049         * Value selection
050         * 
051         * @param solution
052         *            current solution
053         * @param selectedVariable
054         *            selected variable
055         */
056        public T selectValue(Solution<V, T> solution, V selectedVariable);
057    }