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} which halts after a given amount computation time.
031     * 
032     * @param <I>
033     *            the individuals' type
034     * 
035     * @author <a href="http://kumpe.de/christian/java">Christian Kumpe</a>
036     */
037    public final class ComputingTimeLimitHalter<I> implements Halter<I>, Stoppable {
038            private static final long serialVersionUID = 1L;
039            private static final Log log = LogFactory
040                            .getLog(ComputingTimeLimitHalter.class);
041    
042            private final long limit;
043            private transient long firstCycle;
044    
045            private volatile boolean stop = false;
046    
047            /**
048             * Creates a new {@link ComputingTimeLimitHalter} halting after the
049             * specified number of nanoseconds.
050             * 
051             * @param limit
052             *            the allowed computation time in nanoseconds
053             */
054            public ComputingTimeLimitHalter(final long limit) {
055                    if (log.isDebugEnabled()) {
056                            log.debug(format(
057                                            "Constructing new EvaluationLimitHalter which halts after %d ns.",
058                                            limit));
059                    }
060    
061                    this.limit = limit;
062            }
063    
064            @Override
065            public boolean halt(final Collection<EvaluationResult<I>> evaluationResults) {
066                    final long now = System.nanoTime();
067                    if (firstCycle <= 0) {
068                            firstCycle = now;
069                    }
070                    return stop || limit < now - firstCycle;
071            }
072    
073            @Override
074            public void stop() {
075                    stop = true;
076            }
077    
078            @Override
079            public String toString() {
080                    return "EvaluationLimitHalter [limit=" + limit + "]";
081            }
082    }