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Java example source code file (BisectionSolver.java)

This example Java source code file (BisectionSolver.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.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractunivariatesolver, bisectionsolver, default_absolute_accuracy, override, toomanyevaluationsexception

The BisectionSolver.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;

import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.exception.TooManyEvaluationsException;

/**
 * Implements the <a href="http://mathworld.wolfram.com/Bisection.html">
 * bisection algorithm</a> for finding zeros of univariate real functions.
 * <p>
 * The function should be continuous but not necessarily smooth.</p>
 *
 */
public class BisectionSolver extends AbstractUnivariateSolver {
    /** Default absolute accuracy. */
    private static final double DEFAULT_ABSOLUTE_ACCURACY = 1e-6;

    /**
     * Construct a solver with default accuracy (1e-6).
     */
    public BisectionSolver() {
        this(DEFAULT_ABSOLUTE_ACCURACY);
    }
    /**
     * Construct a solver.
     *
     * @param absoluteAccuracy Absolute accuracy.
     */
    public BisectionSolver(double absoluteAccuracy) {
        super(absoluteAccuracy);
    }
    /**
     * Construct a solver.
     *
     * @param relativeAccuracy Relative accuracy.
     * @param absoluteAccuracy Absolute accuracy.
     */
    public BisectionSolver(double relativeAccuracy,
                           double absoluteAccuracy) {
        super(relativeAccuracy, absoluteAccuracy);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected double doSolve()
        throws TooManyEvaluationsException {
        double min = getMin();
        double max = getMax();
        verifyInterval(min, max);
        final double absoluteAccuracy = getAbsoluteAccuracy();
        double m;
        double fm;
        double fmin;

        while (true) {
            m = UnivariateSolverUtils.midpoint(min, max);
            fmin = computeObjectiveValue(min);
            fm = computeObjectiveValue(m);

            if (fm * fmin > 0) {
                // max and m bracket the root.
                min = m;
            } else {
                // min and m bracket the root.
                max = m;
            }

            if (FastMath.abs(max - min) <= absoluteAccuracy) {
                m = UnivariateSolverUtils.midpoint(min, max);
                return m;
            }
        }
    }
}

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