001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.commons.math3.analysis.solvers;
019    
020    /**
021     * Implements the <em>Pegasus</em> method for root-finding (approximating
022     * a zero of a univariate real function). It is a modified
023     * {@link RegulaFalsiSolver <em>Regula Falsi</em>} method.
024     *
025     * <p>Like the <em>Regula Falsi</em> method, convergence is guaranteed by
026     * maintaining a bracketed solution. The <em>Pegasus</em> method however,
027     * should converge much faster than the original <em>Regula Falsi</em>
028     * method. Furthermore, this implementation of the <em>Pegasus</em> method
029     * should not suffer from the same implementation issues as the <em>Regula
030     * Falsi</em> method, which may fail to convergence in certain cases. Also,
031     * the <em>Pegasus</em> method should converge faster than the
032     * {@link IllinoisSolver <em>Illinois</em>} method, another <em>Regula
033     * Falsi</em>-based method.</p>
034     *
035     * <p>The <em>Pegasus</em> method assumes that the function is continuous,
036     * but not necessarily smooth.</p>
037     *
038     * <p>Implementation based on the following article: M. Dowell and P. Jarratt,
039     * <em>The "Pegasus" method for computing the root of an equation</em>,
040     * BIT Numerical Mathematics, volume 12, number 4, pages 503-508, Springer,
041     * 1972.</p>
042     *
043     * @since 3.0
044     * @version $Id: PegasusSolver.java 1364387 2012-07-22 18:14:11Z tn $
045     */
046    public class PegasusSolver extends BaseSecantSolver {
047    
048        /** Construct a solver with default accuracy (1e-6). */
049        public PegasusSolver() {
050            super(DEFAULT_ABSOLUTE_ACCURACY, Method.PEGASUS);
051        }
052    
053        /**
054         * Construct a solver.
055         *
056         * @param absoluteAccuracy Absolute accuracy.
057         */
058        public PegasusSolver(final double absoluteAccuracy) {
059            super(absoluteAccuracy, Method.PEGASUS);
060        }
061    
062        /**
063         * Construct a solver.
064         *
065         * @param relativeAccuracy Relative accuracy.
066         * @param absoluteAccuracy Absolute accuracy.
067         */
068        public PegasusSolver(final double relativeAccuracy,
069                             final double absoluteAccuracy) {
070            super(relativeAccuracy, absoluteAccuracy, Method.PEGASUS);
071        }
072    
073        /**
074         * Construct a solver.
075         *
076         * @param relativeAccuracy Relative accuracy.
077         * @param absoluteAccuracy Absolute accuracy.
078         * @param functionValueAccuracy Maximum function value error.
079         */
080        public PegasusSolver(final double relativeAccuracy,
081                             final double absoluteAccuracy,
082                             final double functionValueAccuracy) {
083            super(relativeAccuracy, absoluteAccuracy, functionValueAccuracy, Method.PEGASUS);
084        }
085    }