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 */ 017package org.apache.commons.math3.genetics; 018 019import java.util.concurrent.TimeUnit; 020 021import 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 * @since 3.1 031 */ 032public class FixedElapsedTime implements StoppingCondition { 033 /** Maximum allowed time period (in nanoseconds). */ 034 private final long maxTimePeriod; 035 036 /** The predetermined termination time (stopping condition). */ 037 private long endTime = -1; 038 039 /** 040 * Create a new {@link FixedElapsedTime} instance. 041 * 042 * @param maxTime maximum number of seconds generations are allowed to evolve 043 * @throws NumberIsTooSmallException if the provided time is < 0 044 */ 045 public FixedElapsedTime(final long maxTime) throws NumberIsTooSmallException { 046 this(maxTime, TimeUnit.SECONDS); 047 } 048 049 /** 050 * Create a new {@link FixedElapsedTime} instance. 051 * 052 * @param maxTime maximum time generations are allowed to evolve 053 * @param unit {@link TimeUnit} of the maxTime argument 054 * @throws NumberIsTooSmallException if the provided time is < 0 055 */ 056 public FixedElapsedTime(final long maxTime, final TimeUnit unit) throws NumberIsTooSmallException { 057 if (maxTime < 0) { 058 throw new NumberIsTooSmallException(maxTime, 0, true); 059 } 060 maxTimePeriod = unit.toNanos(maxTime); 061 } 062 063 /** 064 * Determine whether or not the maximum allowed time has passed. 065 * The termination time is determined after the first generation. 066 * 067 * @param population ignored (no impact on result) 068 * @return <code>true</code> IFF the maximum allowed time period has elapsed 069 */ 070 public boolean isSatisfied(final Population population) { 071 if (endTime < 0) { 072 endTime = System.nanoTime() + maxTimePeriod; 073 } 074 075 return System.nanoTime() >= endTime; 076 } 077}