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 the specified number of cycles.
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 CountingHalter<I> implements Halter<I>, Stoppable {
038            private static final long serialVersionUID = 1L;
039            private static final Log log = LogFactory.getLog(CountingHalter.class);
040    
041            private final int nrOfCycles;
042            private int currentCycle;
043    
044            private volatile boolean stop = false;
045    
046            /**
047             * Creates a new {@link CountingHalter} which halts after the specified
048             * number of cycles.
049             * 
050             * @param nrOfCycles
051             *            the number of cycles after which the {@link CountingHalter}
052             *            will halt
053             */
054            public CountingHalter(final int nrOfCycles) {
055                    if (0 > nrOfCycles) {
056                            throw new IllegalArgumentException("nrOfCycles may not be negative");
057                    }
058    
059                    if (log.isDebugEnabled()) {
060                            log.debug(format(
061                                            "Constructing new CountingHalter which halts after %d cycles.",
062                                            nrOfCycles));
063                    }
064    
065                    this.nrOfCycles = nrOfCycles;
066            }
067    
068            @Override
069            public boolean halt(final Collection<EvaluationResult<I>> evaluationResults) {
070                    if (log.isTraceEnabled()) {
071                            log.trace(format("Checking for halt in cycle %d of %d total.",
072                                            currentCycle, nrOfCycles));
073                    }
074                    ++currentCycle;
075                    return stop || currentCycle > nrOfCycles;
076            }
077    
078            public int getNrOfCycles() {
079                    return nrOfCycles;
080            }
081    
082            public int getCurrentCycle() {
083                    return currentCycle;
084            }
085    
086            @Override
087            public void stop() {
088                    stop = true;
089            }
090    
091            @Override
092            public String toString() {
093                    return "CountingHalter [nrOfCycles=" + nrOfCycles + "]";
094            }
095    }