001    /*
002     * Copyright 2011 Christian Kumpe http://kumpe.de/christian/java
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     *     http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    package de.kumpe.hadooptimizer;
017    
018    import java.io.Serializable;
019    
020    /**
021     * An {@link Evaluator} calculates the <em>evaluation</em> (fitness) of a given
022     * individual as a single <code>double</code>-value.
023     * 
024     * @param <I>
025     *            the individuals' type
026     * 
027     * @author <a href="http://kumpe.de/christian/java">Christian Kumpe</a>
028     */
029    public interface Evaluator<I> extends Serializable {
030            /**
031             * Calculates the evaluation (fitness) of the given {@code individual}.
032             * <p>
033             * A <em>smaller</em> value means <em>better</em> fitness.
034             * 
035             * @param individual
036             *            the individual to calculate the evaluation (fitness)
037             * 
038             * @return the evaluation (fitness) of the given {@code individual}
039             */
040            double evaluate(I individual);
041    }