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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.analysis;
18  
19  import org.apache.commons.math.ConvergenceException;
20  import org.apache.commons.math.FunctionEvaluationException;
21  
22  /**
23   * Interface for univariate real integration algorithms.
24   *  
25   * @version $Revision: 620312 $ $Date: 2008-02-10 12:28:59 -0700 (Sun, 10 Feb 2008) $
26   * @since 1.2
27   */
28  public interface UnivariateRealIntegrator {
29  
30      /**
31       * Set the upper limit for the number of iterations.
32       * <p>
33       * Usually a high iteration count indicates convergence problem. However,
34       * the "reasonable value" varies widely for different cases.  Users are
35       * advised to use the default value.</p>
36       * <p>
37       * A <code>ConvergenceException</code> will be thrown if this number
38       * is exceeded.</p>
39       *  
40       * @param count maximum number of iterations
41       */
42      void setMaximalIterationCount(int count);
43  
44      /**
45       * Get the upper limit for the number of iterations.
46       * 
47       * @return the actual upper limit
48       */
49      int getMaximalIterationCount();
50  
51      /**
52       * Reset the upper limit for the number of iterations to the default.
53       * <p>
54       * The default value is supplied by the implementation.</p>
55       * 
56       * @see #setMaximalIterationCount(int)
57       */
58      void resetMaximalIterationCount();
59  
60      /**
61       * Set the lower limit for the number of iterations.
62       * <p>
63       * Minimal iteration is needed to avoid false early convergence, e.g.
64       * the sample points happen to be zeroes of the function. Users can
65       * use the default value or choose one that they see as appropriate.</p>
66       * <p>
67       * A <code>ConvergenceException</code> will be thrown if this number
68       * is not met.</p>
69       *
70       * @param count minimum number of iterations
71       */
72      void setMinimalIterationCount(int count);
73  
74      /**
75       * Get the lower limit for the number of iterations.
76       * 
77       * @return the actual lower limit
78       */
79      int getMinimalIterationCount();
80  
81      /**
82       * Reset the lower limit for the number of iterations to the default.
83       * <p>
84       * The default value is supplied by the implementation.</p>
85       * 
86       * @see #setMinimalIterationCount(int)
87       */
88      void resetMinimalIterationCount();
89  
90      /**
91       * Set the relative accuracy.
92       * <p>
93       * This is used to stop iterations.</p>
94       * 
95       * @param accuracy the relative accuracy
96       * @throws IllegalArgumentException if the accuracy can't be achieved
97       * or is otherwise deemed unreasonable
98       */
99      void setRelativeAccuracy(double accuracy);
100 
101     /**
102      * Get the actual relative accuracy.
103      *
104      * @return the accuracy
105      */
106     double getRelativeAccuracy();
107 
108     /**
109      * Reset the relative accuracy to the default.
110      * <p>
111      * The default value is provided by the implementation.</p>
112      *
113      * @see #setRelativeAccuracy(double)
114      */
115     void resetRelativeAccuracy();
116 
117     /**
118      * Integrate the function in the given interval.
119      * 
120      * @param min the lower bound for the interval
121      * @param max the upper bound for the interval
122      * @return the value of integral
123      * @throws ConvergenceException if the maximum iteration count is exceeded
124      * or the integrator detects convergence problems otherwise
125      * @throws FunctionEvaluationException if an error occurs evaluating the
126      * function
127      * @throws IllegalArgumentException if min > max or the endpoints do not
128      * satisfy the requirements specified by the integrator
129      */
130     double integrate(double min, double max) throws ConvergenceException, 
131         FunctionEvaluationException, IllegalArgumentException;
132 
133     /**
134      * Get the result of the last run of the integrator.
135      * 
136      * @return the last result
137      * @throws IllegalStateException if there is no result available, either
138      * because no result was yet computed or the last attempt failed
139      */
140     double getResult() throws IllegalStateException;
141 
142     /**
143      * Get the number of iterations in the last run of the integrator.
144      * <p>
145      * This is mainly meant for testing purposes. It may occasionally
146      * help track down performance problems: if the iteration count
147      * is notoriously high, check whether the function is evaluated
148      * properly, and whether another integrator is more amenable to the
149      * problem.</p>
150      * 
151      * @return the last iteration count
152      * @throws IllegalStateException if there is no result available, either
153      * because no result was yet computed or the last attempt failed
154      */
155     int getIterationCount() throws IllegalStateException;
156 }