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The constraint solver library contains a local search based framework that allows modeling of a problem using constraint programming primitives (variables, values, constraints).
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package org.cpsolver.exam.criteria;

import java.util.Collection;
import java.util.Map;
import java.util.Set;

import org.cpsolver.exam.model.Exam;
import org.cpsolver.exam.model.ExamPeriodPlacement;
import org.cpsolver.exam.model.ExamPlacement;
import org.cpsolver.ifs.assignment.Assignment;
import org.cpsolver.ifs.util.DataProperties;


/**
 * A weight for period penalty (used in
 * {@link ExamPeriodPlacement#getPenalty()} multiplied by examination size
 * {@link Exam#getSize()}. Can be set by problem property
 * Exams.PeriodSizeWeight, or in the input xml file, property periodSizeWeight).
 * 
 * 

 * 
 * @author  Tomas Muller
 * @version ExamTT 1.3 (Examination Timetabling)

 *          Copyright (C) 2008 - 2014 Tomas Muller

 *          [email protected]

 *          http://muller.unitime.org

 * 

 *          This library is free software; you can redistribute it and/or modify
 *          it under the terms of the GNU Lesser General Public License as
 *          published by the Free Software Foundation; either version 3 of the
 *          License, or (at your option) any later version. 

 * 

 *          This library is distributed in the hope that it will be useful, but
 *          WITHOUT ANY WARRANTY; without even the implied warranty of
 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *          Lesser General Public License for more details. 

 * 

 *          You should have received a copy of the GNU Lesser General Public
 *          License along with this library; if not see
 *          http://www.gnu.org/licenses/.
 */
public class PeriodSizePenalty extends ExamCriterion {
    
    @Override
    public String getWeightName() {
        return "Exams.PeriodSizeWeight";
    }
    
    @Override
    public String getXmlWeightName() {
        return "periodSizeWeight";
    }
    
    @Override
    public double getWeightDefault(DataProperties config) {
        return 1.0;
    }
    
    @Override
    public double getValue(Assignment assignment, ExamPlacement value, Set conflicts) {
        return value.getPeriodPlacement().getPenalty() * (value.variable().getSize() + 1);
    }
    
    @Override
    public String getName() {
        return "Period×Size Penalty";
    }
    
    @Override
    public double[] getBounds(Assignment assignment, Collection variables) {
        double[] bounds = new double[] { 0.0, 0.0 };
        for (Exam exam : variables) {
            if (!exam.getPeriodPlacements().isEmpty()) {
                int minSizePenalty = Integer.MAX_VALUE, maxSizePenalty = Integer.MIN_VALUE;
                for (ExamPeriodPlacement periodPlacement : exam.getPeriodPlacements()) {
                    minSizePenalty = Math.min(minSizePenalty, periodPlacement.getPenalty() * (exam.getSize() + 1));
                    maxSizePenalty = Math.max(maxSizePenalty, periodPlacement.getPenalty() * (exam.getSize() + 1));
                }
                bounds[0] += minSizePenalty;
                bounds[1] += maxSizePenalty;
            }
        }
        return bounds;
    }
    
    @Override
    public void getInfo(Assignment assignment, Map info) {
        if (getValue(assignment) != 0.0) {
            info.put(getName(), sDoubleFormat.format(getValue(assignment) / assignment.nrAssignedVariables()));
        }
    }

    @Override
    public String toString(Assignment assignment) {
        return "PS:" + sDoubleFormat.format(getValue(assignment) / assignment.nrAssignedVariables());
    }
}