    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    }