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.impl;
017    
018    import static java.lang.String.*;
019    
020    import java.util.Collection;
021    
022    import org.apache.commons.logging.Log;
023    import org.apache.commons.logging.LogFactory;
024    
025    import de.kumpe.hadooptimizer.EvaluationResult;
026    import de.kumpe.hadooptimizer.Halter;
027    import de.kumpe.hadooptimizer.Stoppable;
028    
029    /**
030     * A {@link Halter} halting the evolution process when the evaluation has gone
031     * below a given level.
032     * 
033     * @param <I>
034     *            the individuals' type
035     * 
036     * @author <a href="http://kumpe.de/christian/java">Christian Kumpe</a>
037     */
038    public final class EvaluationLimitHalter<I> implements Halter<I>, Stoppable {
039            private static final long serialVersionUID = 1L;
040            private static final Log log = LogFactory
041                            .getLog(EvaluationLimitHalter.class);
042    
043            private final double limit;
044    
045            private volatile boolean stop = false;
046    
047            /**
048             * Creates a new {@link EvaluationLimitHalter} halting at the given
049             * evaluation value.
050             * 
051             * @param limit
052             *            the evaluation value to reach before halting
053             */
054            public EvaluationLimitHalter(final double limit) {
055                    if (log.isDebugEnabled()) {
056                            log.debug(format(
057                                            "Constructing new EvaluationLimitHalter which halts after a evaluation of %f is reached.",
058                                            limit));
059                    }
060    
061                    this.limit = limit;
062            }
063    
064            @Override
065            public boolean halt(final Collection<EvaluationResult<I>> evaluationResults) {
066                    return stop
067                                    || limit >= evaluationResults.iterator().next().getEvaluation();
068            }
069    
070            @Override
071            public void stop() {
072                    stop = true;
073            }
074    
075            @Override
076            public String toString() {
077                    return "EvaluationLimitHalter [limit=" + limit + "]";
078            }
079    }