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    import org.apache.commons.math3.analysis.DifferentiableUnivariateFunction;
021    import org.apache.commons.math3.util.FastMath;
022    import 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
034    public 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    }