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+/*
+ * 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.analysis.differentiation.DerivativeStructure;
+import org.apache.commons.math3.analysis.differentiation.UnivariateDifferentiableFunction;
+import org.apache.commons.math3.util.FastMath;
+import org.apache.commons.math3.exception.TooManyEvaluationsException;
+
+/**
+ * Implements <a href="http://mathworld.wolfram.com/NewtonsMethod.html">
+ * Newton's Method</a> for finding zeros of real univariate differentiable
+ * functions.
+ *
+ * @since 3.1
+ */
+public class NewtonRaphsonSolver extends AbstractUnivariateDifferentiableSolver {
+ /** Default absolute accuracy. */
+ private static final double DEFAULT_ABSOLUTE_ACCURACY = 1e-6;
+
+ /**
+ * Construct a solver.
+ */
+ public NewtonRaphsonSolver() {
+ this(DEFAULT_ABSOLUTE_ACCURACY);
+ }
+ /**
+ * Construct a solver.
+ *
+ * @param absoluteAccuracy Absolute accuracy.
+ */
+ public NewtonRaphsonSolver(double absoluteAccuracy) {
+ super(absoluteAccuracy);
+ }
+
+ /**
+ * Find a zero near the midpoint of {@code min} and {@code max}.
+ *
+ * @param f Function to solve.
+ * @param min Lower bound for the interval.
+ * @param max Upper bound for the interval.
+ * @param maxEval Maximum number of evaluations.
+ * @return the value where the function is zero.
+ * @throws org.apache.commons.math3.exception.TooManyEvaluationsException
+ * if the maximum evaluation count is exceeded.
+ * @throws org.apache.commons.math3.exception.NumberIsTooLargeException
+ * if {@code min >= max}.
+ */
+ @Override
+ public double solve(int maxEval, final UnivariateDifferentiableFunction f,
+ final double min, final double max)
+ throws TooManyEvaluationsException {
+ return super.solve(maxEval, f, UnivariateSolverUtils.midpoint(min, max));
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ @Override
+ protected double doSolve()
+ throws TooManyEvaluationsException {
+ final double startValue = getStartValue();
+ final double absoluteAccuracy = getAbsoluteAccuracy();
+
+ double x0 = startValue;
+ double x1;
+ while (true) {
+ final DerivativeStructure y0 = computeObjectiveValueAndDerivative(x0);
+ x1 = x0 - (y0.getValue() / y0.getPartialDerivative(1));
+ if (FastMath.abs(x1 - x0) <= absoluteAccuracy) {
+ return x1;
+ }
+
+ x0 = x1;
+ }
+ }
+}