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.MathException;
20  import junit.framework.TestCase;
21  
22  /**
23   * Testcase for Romberg integrator.
24   * <p>
25   * Romberg algorithm is very fast for good behavior integrand. Test runs
26   * show that for a default relative accuracy of 1E-6, it generally takes
27   * takes less than 5 iterations for the integral to converge.
28   * 
29   * @version $Revision: 480442 $ $Date: 2006-11-29 00:21:22 -0700 (Wed, 29 Nov 2006) $ 
30   */
31  public final class RombergIntegratorTest extends TestCase {
32  
33      /**
34       * Test of integrator for the sine function.
35       */
36      public void testSinFunction() throws MathException {
37          UnivariateRealFunction f = new SinFunction();
38          UnivariateRealIntegrator integrator = new RombergIntegrator(f);
39          double min, max, expected, result, tolerance;
40  
41          min = 0; max = Math.PI; expected = 2;
42          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
43          result = integrator.integrate(min, max);
44          assertEquals(expected, result, tolerance);
45  
46          min = -Math.PI/3; max = 0; expected = -0.5;
47          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
48          result = integrator.integrate(min, max);
49          assertEquals(expected, result, tolerance);
50      }
51  
52      /**
53       * Test of integrator for the quintic function.
54       */
55      public void testQuinticFunction() throws MathException {
56          UnivariateRealFunction f = new QuinticFunction();
57          UnivariateRealIntegrator integrator = new RombergIntegrator(f);
58          double min, max, expected, result, tolerance;
59  
60          min = 0; max = 1; expected = -1.0/48;
61          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
62          result = integrator.integrate(min, max);
63          assertEquals(expected, result, tolerance);
64  
65          min = 0; max = 0.5; expected = 11.0/768;
66          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
67          result = integrator.integrate(min, max);
68          assertEquals(expected, result, tolerance);
69  
70          min = -1; max = 4; expected = 2048/3.0 - 78 + 1.0/48;
71          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
72          result = integrator.integrate(min, max);
73          assertEquals(expected, result, tolerance);
74      }
75  
76      /**
77       * Test of parameters for the integrator.
78       */
79      public void testParameters() throws Exception {
80          UnivariateRealFunction f = new SinFunction();
81          UnivariateRealIntegrator integrator = new RombergIntegrator(f);
82  
83          try {
84              // bad interval
85              integrator.integrate(1, -1);
86              fail("Expecting IllegalArgumentException - bad interval");
87          } catch (IllegalArgumentException ex) {
88              // expected
89          }
90          try {
91              // bad iteration limits
92              integrator.setMinimalIterationCount(5);
93              integrator.setMaximalIterationCount(4);
94              integrator.integrate(-1, 1);
95              fail("Expecting IllegalArgumentException - bad iteration limits");
96          } catch (IllegalArgumentException ex) {
97              // expected
98          }
99          try {
100             // bad iteration limits
101             integrator.setMinimalIterationCount(10);
102             integrator.setMaximalIterationCount(50);
103             integrator.integrate(-1, 1);
104             fail("Expecting IllegalArgumentException - bad iteration limits");
105         } catch (IllegalArgumentException ex) {
106             // expected
107         }
108     }
109 }