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Java example source code file (RegulaFalsiSolver.java)

This example Java source code file (RegulaFalsiSolver.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

basesecantsolver, regulafalsisolver

The RegulaFalsiSolver.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.math3.analysis.solvers;

/**
 * Implements the <em>Regula Falsi or False position method for
 * root-finding (approximating a zero of a univariate real function). It is a
 * modified {@link SecantSolver <em>Secant} method.
 *
 * <p>The Regula Falsi method is included for completeness, for
 * testing purposes, for educational purposes, for comparison to other
 * algorithms, etc. It is however <strong>not intended to be used
 * for actual problems, as one of the bounds often remains fixed, resulting
 * in very slow convergence. Instead, one of the well-known modified
 * <em>Regula Falsi algorithms can be used ({@link IllinoisSolver
 * <em>Illinois} or {@link PegasusSolver Pegasus}). These two
 * algorithms solve the fundamental issues of the original <em>Regula
 * Falsi</em> algorithm, and greatly out-performs it for most, if not all,
 * (practical) functions.
 *
 * <p>Unlike the Secant method, the Regula Falsi guarantees
 * convergence, by maintaining a bracketed solution. Note however, that due to
 * the finite/limited precision of Java's {@link Double double} type, which is
 * used in this implementation, the algorithm may get stuck in a situation
 * where it no longer makes any progress. Such cases are detected and result
 * in a {@code ConvergenceException} exception being thrown. In other words,
 * the algorithm theoretically guarantees convergence, but the implementation
 * does not.</p>
 *
 * <p>The Regula Falsi method assumes that the function is continuous,
 * but not necessarily smooth.</p>
 *
 * <p>Implementation based on the following article: M. Dowell and P. Jarratt,
 * <em>A modified regula falsi method for computing the root of an
 * equation</em>, BIT Numerical Mathematics, volume 11, number 2,
 * pages 168-174, Springer, 1971.</p>
 *
 * @since 3.0
 */
public class RegulaFalsiSolver extends BaseSecantSolver {

    /** Construct a solver with default accuracy (1e-6). */
    public RegulaFalsiSolver() {
        super(DEFAULT_ABSOLUTE_ACCURACY, Method.REGULA_FALSI);
    }

    /**
     * Construct a solver.
     *
     * @param absoluteAccuracy Absolute accuracy.
     */
    public RegulaFalsiSolver(final double absoluteAccuracy) {
        super(absoluteAccuracy, Method.REGULA_FALSI);
    }

    /**
     * Construct a solver.
     *
     * @param relativeAccuracy Relative accuracy.
     * @param absoluteAccuracy Absolute accuracy.
     */
    public RegulaFalsiSolver(final double relativeAccuracy,
                             final double absoluteAccuracy) {
        super(relativeAccuracy, absoluteAccuracy, Method.REGULA_FALSI);
    }

    /**
     * Construct a solver.
     *
     * @param relativeAccuracy Relative accuracy.
     * @param absoluteAccuracy Absolute accuracy.
     * @param functionValueAccuracy Maximum function value error.
     */
    public RegulaFalsiSolver(final double relativeAccuracy,
                             final double absoluteAccuracy,
                             final double functionValueAccuracy) {
        super(relativeAccuracy, absoluteAccuracy, functionValueAccuracy, Method.REGULA_FALSI);
    }
}

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