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
18 package org.apache.commons.math4.legacy.optim;
19
20 /**
21 * This interface specifies how to check if an optimization algorithm has
22 * converged.
23 * <br>
24 * Deciding if convergence has been reached is a problem-dependent issue. The
25 * user should provide a class implementing this interface to allow the
26 * optimization algorithm to stop its search according to the problem at hand.
27 * <br>
28 * For convenience, three implementations that fit simple needs are already
29 * provided: {@link SimpleValueChecker}, {@link SimpleVectorValueChecker} and
30 * {@link SimplePointChecker}. The first two consider that convergence is
31 * reached when the objective function value does not change much anymore, it
32 * does not use the point set at all.
33 * The third one considers that convergence is reached when the input point
34 * set does not change much anymore, it does not use objective function value
35 * at all.
36 *
37 * @param <PAIR> Type of the (point, objective value) pair.
38 *
39 * @see org.apache.commons.math4.legacy.optim.SimplePointChecker
40 * @see org.apache.commons.math4.legacy.optim.SimpleValueChecker
41 * @see org.apache.commons.math4.legacy.optim.SimpleVectorValueChecker
42 *
43 * @since 3.0
44 */
45 public interface ConvergenceChecker<PAIR> extends OptimizationData {
46 /**
47 * Check if the optimization algorithm has converged.
48 *
49 * @param iteration Current iteration.
50 * @param previous Best point in the previous iteration.
51 * @param current Best point in the current iteration.
52 * @return {@code true} if the algorithm is considered to have converged.
53 */
54 boolean converged(int iteration, PAIR previous, PAIR current);
55 }