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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.genetics;
import java.util.concurrent.TimeUnit;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
/**
* Stops after a fixed amount of time has elapsed.
*
* The first time {@link #isSatisfied(Population)} is invoked, the end time of the evolution is determined based on the
* provided maxTime value. Once the elapsed time reaches the configured maxTime value,
* {@link #isSatisfied(Population)} returns true.
*
* @since 3.1
*/
public class FixedElapsedTime implements StoppingCondition {
/** Maximum allowed time period (in nanoseconds). */
private final long maxTimePeriod;
/** The predetermined termination time (stopping condition). */
private long endTime = -1;
/**
* Create a new {@link FixedElapsedTime} instance.
*
* @param maxTime maximum number of seconds generations are allowed to evolve
* @throws NumberIsTooSmallException if the provided time is < 0
*/
public FixedElapsedTime(final long maxTime) throws NumberIsTooSmallException {
this(maxTime, TimeUnit.SECONDS);
}
/**
* Create a new {@link FixedElapsedTime} instance.
*
* @param maxTime maximum time generations are allowed to evolve
* @param unit {@link TimeUnit} of the maxTime argument
* @throws NumberIsTooSmallException if the provided time is < 0
*/
public FixedElapsedTime(final long maxTime, final TimeUnit unit) throws NumberIsTooSmallException {
if (maxTime < 0) {
throw new NumberIsTooSmallException(maxTime, 0, true);
}
maxTimePeriod = unit.toNanos(maxTime);
}
/**
* Determine whether or not the maximum allowed time has passed.
* The termination time is determined after the first generation.
*
* @param population ignored (no impact on result)
* @return true IFF the maximum allowed time period has elapsed
*/
public boolean isSatisfied(final Population population) {
if (endTime < 0) {
endTime = System.nanoTime() + maxTimePeriod;
}
return System.nanoTime() >= endTime;
}
}