001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.math3.genetics;
018
019 import java.util.concurrent.TimeUnit;
020
021 import org.apache.commons.math3.exception.NumberIsTooSmallException;
022
023 /**
024 * Stops after a fixed amount of time has elapsed.
025 * <p>
026 * The first time {@link #isSatisfied(Population)} is invoked, the end time of the evolution is determined based on the
027 * provided <code>maxTime</code> value. Once the elapsed time reaches the configured <code>maxTime</code> value,
028 * {@link #isSatisfied(Population)} returns true.
029 *
030 * @version $Id: FixedElapsedTime.java 1385297 2012-09-16 16:05:57Z tn $
031 * @since 3.1
032 */
033 public class FixedElapsedTime implements StoppingCondition {
034 /** Maximum allowed time period (in nanoseconds). */
035 private final long maxTimePeriod;
036
037 /** The predetermined termination time (stopping condition). */
038 private long endTime = -1;
039
040 /**
041 * Create a new {@link FixedElapsedTime} instance.
042 *
043 * @param maxTime maximum number of seconds generations are allowed to evolve
044 * @throws NumberIsTooSmallException if the provided time is < 0
045 */
046 public FixedElapsedTime(final long maxTime) throws NumberIsTooSmallException {
047 this(maxTime, TimeUnit.SECONDS);
048 }
049
050 /**
051 * Create a new {@link FixedElapsedTime} instance.
052 *
053 * @param maxTime maximum time generations are allowed to evolve
054 * @param unit {@link TimeUnit} of the maxTime argument
055 * @throws NumberIsTooSmallException if the provided time is < 0
056 */
057 public FixedElapsedTime(final long maxTime, final TimeUnit unit) throws NumberIsTooSmallException {
058 if (maxTime < 0) {
059 throw new NumberIsTooSmallException(maxTime, 0, true);
060 }
061 maxTimePeriod = unit.toNanos(maxTime);
062 }
063
064 /**
065 * Determine whether or not the maximum allowed time has passed.
066 * The termination time is determined after the first generation.
067 *
068 * @param population ignored (no impact on result)
069 * @return <code>true</code> IFF the maximum allowed time period has elapsed
070 */
071 public boolean isSatisfied(final Population population) {
072 if (endTime < 0) {
073 endTime = System.nanoTime() + maxTimePeriod;
074 }
075
076 return System.nanoTime() >= endTime;
077 }
078 }