1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.math; 18 19 20 /** 21 * Interface for algorithms handling convergence settings. 22 * <p> 23 * This interface only deals with convergence parameters setting, not 24 * execution of the algorithms per se. 25 * </p> 26 * @see ConvergenceException 27 * @version $Revision: 785473 $ $Date: 2009-06-17 00:02:35 -0400 (Wed, 17 Jun 2009) $ 28 * @since 2.0 29 */ 30 public interface ConvergingAlgorithm { 31 32 /** 33 * Set the upper limit for the number of iterations. 34 * <p> 35 * Usually a high iteration count indicates convergence problems. However, 36 * the "reasonable value" varies widely for different algorithms. Users are 37 * advised to use the default value supplied by the algorithm.</p> 38 * <p> 39 * A {@link ConvergenceException} will be thrown if this number 40 * is exceeded.</p> 41 * 42 * @param count maximum number of iterations 43 */ 44 public abstract void setMaximalIterationCount(int count); 45 46 /** 47 * Get the upper limit for the number of iterations. 48 * 49 * @return the actual upper limit 50 */ 51 public abstract int getMaximalIterationCount(); 52 53 /** 54 * Reset the upper limit for the number of iterations to the default. 55 * <p> 56 * The default value is supplied by the algorithm implementation.</p> 57 * 58 * @see #setMaximalIterationCount(int) 59 */ 60 public abstract void resetMaximalIterationCount(); 61 62 /** 63 * Set the absolute accuracy. 64 * <p> 65 * The default is usually chosen so that results in the interval 66 * -10..-0.1 and +0.1..+10 can be found with a reasonable accuracy. If the 67 * expected absolute value of your results is of much smaller magnitude, set 68 * this to a smaller value.</p> 69 * <p> 70 * Algorithms are advised to do a plausibility check with the relative 71 * accuracy, but clients should not rely on this.</p> 72 * 73 * @param accuracy the accuracy. 74 * @throws IllegalArgumentException if the accuracy can't be achieved by 75 * the solver or is otherwise deemed unreasonable. 76 */ 77 public abstract void setAbsoluteAccuracy(double accuracy); 78 79 /** 80 * Get the actual absolute accuracy. 81 * 82 * @return the accuracy 83 */ 84 public abstract double getAbsoluteAccuracy(); 85 86 /** 87 * Reset the absolute accuracy to the default. 88 * <p> 89 * The default value is provided by the algorithm implementation.</p> 90 */ 91 public abstract void resetAbsoluteAccuracy(); 92 93 /** 94 * Set the relative accuracy. 95 * <p> 96 * This is used to stop iterations if the absolute accuracy can't be 97 * achieved due to large values or short mantissa length.</p> 98 * <p> 99 * If this should be the primary criterion for convergence rather then a 100 * safety measure, set the absolute accuracy to a ridiculously small value, 101 * like {@link org.apache.commons.math.util.MathUtils#SAFE_MIN MathUtils.SAFE_MIN}.</p> 102 * 103 * @param accuracy the relative accuracy. 104 * @throws IllegalArgumentException if the accuracy can't be achieved by 105 * the algorithm or is otherwise deemed unreasonable. 106 */ 107 public abstract void setRelativeAccuracy(double accuracy); 108 109 /** 110 * Get the actual relative accuracy. 111 * @return the accuracy 112 */ 113 public abstract double getRelativeAccuracy(); 114 115 /** 116 * Reset the relative accuracy to the default. 117 * The default value is provided by the algorithm implementation. 118 */ 119 public abstract void resetRelativeAccuracy(); 120 121 /** 122 * Get the number of iterations in the last run of the algorithm. 123 * <p> 124 * This is mainly meant for testing purposes. It may occasionally 125 * help track down performance problems: if the iteration count 126 * is notoriously high, check whether the problem is evaluated 127 * properly, and whether another algorithm is more amenable to the 128 * problem.</p> 129 * 130 * @return the last iteration count. 131 * @throws IllegalStateException if there is no result available, either 132 * because no result was yet computed or the last attempt failed. 133 */ 134 public abstract int getIterationCount(); 135 136 }