ConvexC2_DTLZ2.java

/* Copyright 2009-2016 David Hadka
 *
 * This file is part of the MOEA Framework.
 *
 * The MOEA Framework 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.
 *
 * The MOEA Framework 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 the MOEA Framework.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.moeaframework.problem.CDTLZ;

import org.moeaframework.core.Solution;
import org.moeaframework.core.variable.RealVariable;

/**
 * The convex C2-DTLZ2 problem.
 */
public class ConvexC2_DTLZ2 extends ConvexDTLZ2 {

	/**
	 * Constructs a convex C2-DTLZ2 test problem with the specified number of
	 * variables and objectives.
	 * 
	 * @param numberOfVariables the number of variables for this problem
	 * @param numberOfObjectives the number of objectives for this problem
	 */
	public ConvexC2_DTLZ2(int numberOfVariables, int numberOfObjectives) {
		super(numberOfVariables, numberOfObjectives);
	}

	/**
	 * Constructs a convex C2-DTLZ2 test problem with the specified number of
	 * objectives.  This is equivalent to calling
	 * {@code new DTLZ2(numberOfObjectives+9, numberOfObjectives)}.
	 * 
	 * @param numberOfObjectives the number of objectives for this problem
	 */
	public ConvexC2_DTLZ2(int numberOfObjectives) {
		super(numberOfObjectives);
	}
	
	@Override
	public int getNumberOfConstraints() {
		return 1;
	}
	
	@Override
	public Solution newSolution() {
		Solution solution = new Solution(numberOfVariables, numberOfObjectives,
				1);

		for (int i = 0; i < numberOfVariables; i++) {
			solution.setVariable(i, new RealVariable(0.0, 1.0));
		}

		return solution;
	}

	@Override
	public void evaluate(Solution solution) {
		super.evaluate(solution);
		
		double lambda = 0.0;
		double c = 0.0;
		
		for (int i = 0; i < numberOfObjectives; i++) {
			lambda += solution.getObjective(i);
		}
		
		lambda /= numberOfObjectives;
		
		for (int i = 0; i < numberOfObjectives; i++) {
			c += Math.pow(solution.getObjective(i) - lambda, 2.0);
		}
		
		c -= Math.pow(getR(), 2.0);
		
		solution.setConstraint(0, c >= 0 ? 0.0 : c);
	}
	
	private double getR() {
		if (numberOfObjectives <= 5) {
			return 0.225;
		} else if (numberOfObjectives <= 10) {
			return 0.26;
		} else {
			return 0.27;
		}
	}

}