MultiObjectiveFitness.java

/*
 * Encog(tm) Core v3.4 - Java Version
 * http://www.heatonresearch.com/encog/
 * https://github.com/encog/encog-java-core
 
 * Copyright 2008-2016 Heaton Research, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *   
 * For more information on Heaton Research copyrights, licenses 
 * and trademarks visit:
 * http://www.heatonresearch.com/copyright
 */
package org.encog.ml.fitness;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import org.encog.EncogError;
import org.encog.ml.CalculateScore;
import org.encog.ml.MLMethod;

/**
 * A multi-objective fitness function.
 */
public class MultiObjectiveFitness  implements CalculateScore, Serializable {
	
	/**
	 * The serial id.
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * The objectives.
	 */
	private final List<FitnessObjective> objectives = new ArrayList<FitnessObjective>();
	
	/**
	 * Is the goal to minimize the score?
	 */
	private boolean min;

	/**
	 * Add an objective.
	 * @param weight The weight of this objective, 1.0 for full, 0.5 for half, etc.
	 * @param fitnessFunction The fitness function.
	 */
	public void addObjective(double weight, CalculateScore fitnessFunction) {
		if( this.objectives.size()==0 ) {
			this.min = fitnessFunction.shouldMinimize();
		} else {
			if( fitnessFunction.shouldMinimize() != this.min) {
				throw new EncogError("Multi-objective mismatch, some objectives are min and some are max.");
			}
		}
		this.objectives.add(new FitnessObjective(weight,fitnessFunction));
	}
	
	/**
	 * {@inheritDoc}
	 */
	@Override
	public double calculateScore(MLMethod method) {
		double result = 0;
		
		for(FitnessObjective obj: this.objectives) {
			result+=obj.getScore().calculateScore(method) * obj.getWeight();
		}
		
		return result;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public boolean shouldMinimize() {
		return this.min;
	}
	
	/**
	 * {@inheritDoc}
	 */
	@Override
	public boolean requireSingleThreaded() {
		for(FitnessObjective obj: this.objectives) {
			if( obj.getScore().requireSingleThreaded() ) {
				return true;
			}
		}
		return false;
	}

}