1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.math4.legacy.genetics;
18
19 import java.util.concurrent.TimeUnit;
20
21 import org.apache.commons.math4.legacy.exception.NumberIsTooSmallException;
22
23 /**
24 * Stops after a fixed amount of time has elapsed.
25 * <p>
26 * The first time {@link #isSatisfied(Population)} is invoked, the end time of
27 * the evolution is determined based on the provided <code>maxTime</code> value.
28 * Once the elapsed time reaches the configured <code>maxTime</code> value,
29 * {@link #isSatisfied(Population)} returns true.
30 *
31 * @since 3.1
32 */
33 public class FixedElapsedTime implements StoppingCondition {
34 /** Maximum allowed time period (in nanoseconds). */
35 private final long maxTimePeriod;
36
37 /** The predetermined termination time (stopping condition). */
38 private long endTime = -1;
39
40 /**
41 * Create a new {@link FixedElapsedTime} instance.
42 *
43 * @param maxTime maximum number of seconds generations are allowed to evolve
44 * @throws NumberIsTooSmallException if the provided time is < 0
45 */
46 public FixedElapsedTime(final long maxTime) throws NumberIsTooSmallException {
47 this(maxTime, TimeUnit.SECONDS);
48 }
49
50 /**
51 * Create a new {@link FixedElapsedTime} instance.
52 *
53 * @param maxTime maximum time generations are allowed to evolve
54 * @param unit {@link TimeUnit} of the maxTime argument
55 * @throws NumberIsTooSmallException if the provided time is < 0
56 */
57 public FixedElapsedTime(final long maxTime, final TimeUnit unit) throws NumberIsTooSmallException {
58 if (maxTime < 0) {
59 throw new NumberIsTooSmallException(maxTime, 0, true);
60 }
61 maxTimePeriod = unit.toNanos(maxTime);
62 }
63
64 /**
65 * Determine whether or not the maximum allowed time has passed.
66 * The termination time is determined after the first generation.
67 *
68 * @param population ignored (no impact on result)
69 * @return <code>true</code> IFF the maximum allowed time period has elapsed
70 */
71 @Override
72 public boolean isSatisfied(final Population population) {
73 if (endTime < 0) {
74 endTime = System.nanoTime() + maxTimePeriod;
75 }
76
77 return System.nanoTime() >= endTime;
78 }
79 }