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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  }