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/* * Copyright 2003-2004 The Apache Software Foundation. * * Licensed 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.math.analysis; import org.apache.commons.math.ConvergenceException; import org.apache.commons.math.FunctionEvaluationException; /** * Interface for (univariate real) rootfinding algorithms. * <p> * Implementations will search for only one zero in the given interval. * * @version $Revision: 1.14 $ $Date: 2004/07/17 21:19:39 $ */ public interface UnivariateRealSolver { /** * Set the upper limit for the number of iterations. * <p> * Usually a high iteration count indicates convergence problems. However, * the "reasonable value" varies widely for different solvers. Users are * advised to use the default value supplied by the solver. * <p> * A <code>ConvergenceException</code> will be thrown if this number * is exceeded. * * @param count maximum number of iterations */ void setMaximalIterationCount(int count); /** * Get the upper limit for the number of iterations. * * @return the actual upper limit */ int getMaximalIterationCount(); /** * Reset the upper limit for the number of iterations to the default. * <p> * The default value is supplied by the solver implementation. * * @see #setMaximalIterationCount(int) */ void resetMaximalIterationCount(); /** * Set the absolute accuracy. * <p> * The default is usually choosen so that roots in the interval * -10..-0.1 and +0.1..+10 can be found with a reasonable accuracy. If the * expected absolute value of your roots is of much smaller magnitude, set * this to a smaller value. * <p> * Solvers are advised to do a plausibility check with the relative * accuracy, but clients should not rely on this. * * @param accuracy the accuracy. * @throws IllegalArgumentException if the accuracy can't be achieved by * the solver or is otherwise deemed unreasonable. */ void setAbsoluteAccuracy(double accuracy); /** * Get the actual absolute accuracy. * * @return the accuracy */ double getAbsoluteAccuracy(); /** * Reset the absolute accuracy to the default. * <p> * The default value is provided by the solver implementation. */ void resetAbsoluteAccuracy(); /** * Set the relative accuracy. * <p> * This is used to stop iterations if the absolute accuracy can't be * achieved due to large values or short mantissa length. * <p> * If this should be the primary criterion for convergence rather then a * safety measure, set the absolute accuracy to a ridiculously small value, * like 1E-1000. * * @param accuracy the relative accuracy. * @throws IllegalArgumentException if the accuracy can't be achieved by * the solver or is otherwise deemed unreasonable. */ void setRelativeAccuracy(double accuracy); /** * Get the actual relative accuracy. * @return the accuracy */ double getRelativeAccuracy(); /** * Reset the relative accuracy to the default. * The default value is provided by the solver implementation. */ void resetRelativeAccuracy(); /** * Set the function value accuracy. * <p> * This is used to determine whan an evaluated function value or some other * value which is used as divisor is zero. * <p> * This is a safety guard and it shouldn't be necesary to change this in * general. * * @param accuracy the accuracy. * @throws IllegalArgumentException if the accuracy can't be achieved by * the solver or is otherwise deemed unreasonable. */ void setFunctionValueAccuracy(double accuracy); /** * Get the actual function value accuracy. * @return the accuracy */ double getFunctionValueAccuracy(); /** * Reset the actual function accuracy to the default. * The default value is provided by the solver implementation. */ void resetFunctionValueAccuracy(); /** * Solve for a zero root in the given interval. * A solver may require that the interval brackets a single zero root. * * @param min the lower bound for the interval. * @param max the upper bound for the interval. * @return a value where the function is zero * @throws ConvergenceException if the maximum iteration count is exceeded * or the solver detects convergence problems otherwise. * @throws FunctionEvaluationException if an error occurs evaluating the * function * @throws IllegalArgumentException if min > max or the endpoints do not * satisfy the requirements specified by the solver */ double solve(double min, double max) throws ConvergenceException, FunctionEvaluationException; /** * Solve for a zero in the given interval, start at startValue. * A solver may require that the interval brackets a single zero root. * * @param min the lower bound for the interval. * @param max the upper bound for the interval. * @param startValue the start value to use * @return a value where the function is zero * @throws ConvergenceException if the maximum iteration count is exceeded * or the solver detects convergence problems otherwise. * @throws FunctionEvaluationException if an error occurs evaluating the * function * @throws IllegalArgumentException if min > max or the arguments do not * satisfy the requirements specified by the solver */ double solve(double min, double max, double startValue) throws ConvergenceException, FunctionEvaluationException; /** * Get the result of the last run of the solver. * * @return the last result. * @throws IllegalStateException if there is no result available, either * because no result was yet computed or the last attempt failed. */ double getResult(); /** * Get the number of iterations in the last run of the solver. * <p> * This is mainly meant for testing purposes. It may occasionally * help track down performance problems: if the iteration count * is notoriously high, check whether the function is evaluated * properly, and whether another solver is more amenable to the * problem. * * @return the last iteration count. * @throws IllegalStateException if there is no result available, either * because no result was yet computed or the last attempt failed. */ int getIterationCount(); }