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 * https://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 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22
23 package org.hipparchus.analysis.solvers;
24
25 /**
26 * Implements the <em>Pegasus</em> method for root-finding (approximating
27 * a zero of a univariate real function). It is a modified
28 * {@link RegulaFalsiSolver <em>Regula Falsi</em>} method.
29 *
30 * <p>Like the <em>Regula Falsi</em> method, convergence is guaranteed by
31 * maintaining a bracketed solution. The <em>Pegasus</em> method however,
32 * should converge much faster than the original <em>Regula Falsi</em>
33 * method. Furthermore, this implementation of the <em>Pegasus</em> method
34 * should not suffer from the same implementation issues as the <em>Regula
35 * Falsi</em> method, which may fail to convergence in certain cases. Also,
36 * the <em>Pegasus</em> method should converge faster than the
37 * {@link IllinoisSolver <em>Illinois</em>} method, another <em>Regula
38 * Falsi</em>-based method.</p>
39 *
40 * <p>The <em>Pegasus</em> method assumes that the function is continuous,
41 * but not necessarily smooth.</p>
42 *
43 * <p>Implementation based on the following article: M. Dowell and P. Jarratt,
44 * <em>The "Pegasus" method for computing the root of an equation</em>,
45 * BIT Numerical Mathematics, volume 12, number 4, pages 503-508, Springer,
46 * 1972.</p>
47 *
48 */
49 public class PegasusSolver extends BaseSecantSolver {
50
51 /** Construct a solver with default accuracy (1e-6). */
52 public PegasusSolver() {
53 super(DEFAULT_ABSOLUTE_ACCURACY, Method.PEGASUS);
54 }
55
56 /**
57 * Construct a solver.
58 *
59 * @param absoluteAccuracy Absolute accuracy.
60 */
61 public PegasusSolver(final double absoluteAccuracy) {
62 super(absoluteAccuracy, Method.PEGASUS);
63 }
64
65 /**
66 * Construct a solver.
67 *
68 * @param relativeAccuracy Relative accuracy.
69 * @param absoluteAccuracy Absolute accuracy.
70 */
71 public PegasusSolver(final double relativeAccuracy,
72 final double absoluteAccuracy) {
73 super(relativeAccuracy, absoluteAccuracy, Method.PEGASUS);
74 }
75
76 /**
77 * Construct a solver.
78 *
79 * @param relativeAccuracy Relative accuracy.
80 * @param absoluteAccuracy Absolute accuracy.
81 * @param functionValueAccuracy Maximum function value error.
82 */
83 public PegasusSolver(final double relativeAccuracy,
84 final double absoluteAccuracy,
85 final double functionValueAccuracy) {
86 super(relativeAccuracy, absoluteAccuracy, functionValueAccuracy, Method.PEGASUS);
87 }
88 }