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 package org.apache.commons.math.analysis.solvers; 018 019 import org.apache.commons.math.FunctionEvaluationException; 020 import org.apache.commons.math.MaxIterationsExceededException; 021 import org.apache.commons.math.analysis.UnivariateRealFunction; 022 023 /** 024 * Implements the <a href="http://mathworld.wolfram.com/Bisection.html"> 025 * bisection algorithm</a> for finding zeros of univariate real functions. 026 * <p> 027 * The function should be continuous but not necessarily smooth.</p> 028 * 029 * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $ 030 */ 031 public class BisectionSolver extends UnivariateRealSolverImpl { 032 033 /** 034 * Construct a solver for the given function. 035 * 036 * @param f function to solve. 037 * @deprecated as of 2.0 the function to solve is passed as an argument 038 * to the {@link #solve(UnivariateRealFunction, double, double)} or 039 * {@link UnivariateRealSolverImpl#solve(UnivariateRealFunction, double, double, double)} 040 * method. 041 */ 042 @Deprecated 043 public BisectionSolver(UnivariateRealFunction f) { 044 super(f, 100, 1E-6); 045 } 046 047 /** 048 * Construct a solver. 049 * 050 */ 051 public BisectionSolver() { 052 super(100, 1E-6); 053 } 054 055 /** {@inheritDoc} */ 056 @Deprecated 057 public double solve(double min, double max, double initial) 058 throws MaxIterationsExceededException, FunctionEvaluationException { 059 return solve(f, min, max); 060 } 061 062 /** {@inheritDoc} */ 063 @Deprecated 064 public double solve(double min, double max) 065 throws MaxIterationsExceededException, FunctionEvaluationException { 066 return solve(f, min, max); 067 } 068 069 /** {@inheritDoc} */ 070 public double solve(final UnivariateRealFunction f, double min, double max, double initial) 071 throws MaxIterationsExceededException, FunctionEvaluationException { 072 return solve(min, max); 073 } 074 075 /** {@inheritDoc} */ 076 public double solve(final UnivariateRealFunction f, double min, double max) 077 throws MaxIterationsExceededException, FunctionEvaluationException { 078 079 clearResult(); 080 verifyInterval(min,max); 081 double m; 082 double fm; 083 double fmin; 084 085 int i = 0; 086 while (i < maximalIterationCount) { 087 m = UnivariateRealSolverUtils.midpoint(min, max); 088 fmin = f.value(min); 089 fm = f.value(m); 090 091 if (fm * fmin > 0.0) { 092 // max and m bracket the root. 093 min = m; 094 } else { 095 // min and m bracket the root. 096 max = m; 097 } 098 099 if (Math.abs(max - min) <= absoluteAccuracy) { 100 m = UnivariateRealSolverUtils.midpoint(min, max); 101 setResult(m, i); 102 return m; 103 } 104 ++i; 105 } 106 107 throw new MaxIterationsExceededException(maximalIterationCount); 108 } 109 }