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
018package org.apache.commons.math3.analysis.solvers;
019
020import org.apache.commons.math3.analysis.DifferentiableUnivariateFunction;
021import org.apache.commons.math3.util.FastMath;
022import org.apache.commons.math3.exception.TooManyEvaluationsException;
023
024/**
025 * Implements <a href="http://mathworld.wolfram.com/NewtonsMethod.html">
026 * Newton's Method</a> for finding zeros of real univariate functions.
027 * <p>
028 * The function should be continuous but not necessarily smooth.</p>
029 *
030 * @deprecated as of 3.1, replaced by {@link NewtonRaphsonSolver}
031 * @version $Id: NewtonSolver.java 1395937 2012-10-09 10:04:36Z luc $
032 */
033@Deprecated
034public class NewtonSolver extends AbstractDifferentiableUnivariateSolver {
035    /** Default absolute accuracy. */
036    private static final double DEFAULT_ABSOLUTE_ACCURACY = 1e-6;
037
038    /**
039     * Construct a solver.
040     */
041    public NewtonSolver() {
042        this(DEFAULT_ABSOLUTE_ACCURACY);
043    }
044    /**
045     * Construct a solver.
046     *
047     * @param absoluteAccuracy Absolute accuracy.
048     */
049    public NewtonSolver(double absoluteAccuracy) {
050        super(absoluteAccuracy);
051    }
052
053    /**
054     * Find a zero near the midpoint of {@code min} and {@code max}.
055     *
056     * @param f Function to solve.
057     * @param min Lower bound for the interval.
058     * @param max Upper bound for the interval.
059     * @param maxEval Maximum number of evaluations.
060     * @return the value where the function is zero.
061     * @throws org.apache.commons.math3.exception.TooManyEvaluationsException
062     * if the maximum evaluation count is exceeded.
063     * @throws org.apache.commons.math3.exception.NumberIsTooLargeException
064     * if {@code min >= max}.
065     */
066    @Override
067    public double solve(int maxEval, final DifferentiableUnivariateFunction f,
068                        final double min, final double max)
069        throws TooManyEvaluationsException {
070        return super.solve(maxEval, f, UnivariateSolverUtils.midpoint(min, max));
071    }
072
073    /**
074     * {@inheritDoc}
075     */
076    @Override
077    protected double doSolve()
078        throws TooManyEvaluationsException {
079        final double startValue = getStartValue();
080        final double absoluteAccuracy = getAbsoluteAccuracy();
081
082        double x0 = startValue;
083        double x1;
084        while (true) {
085            x1 = x0 - (computeObjectiveValue(x0) / computeDerivativeObjectiveValue(x0));
086            if (FastMath.abs(x1 - x0) <= absoluteAccuracy) {
087                return x1;
088            }
089
090            x0 = x1;
091        }
092    }
093}