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.integration;
18  
19  import org.apache.commons.math.MathException;
20  import org.apache.commons.math.analysis.QuinticFunction;
21  import org.apache.commons.math.analysis.SinFunction;
22  import org.apache.commons.math.analysis.UnivariateRealFunction;
23  
24  import junit.framework.TestCase;
25  
26  /**
27   * Testcase for Simpson integrator.
28   * <p>
29   * Test runs show that for a default relative accuracy of 1E-6, it
30   * generally takes 5 to 10 iterations for the integral to converge.
31   * 
32   * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $ 
33   */
34  public final class SimpsonIntegratorTest extends TestCase {
35  
36      /**
37       * Test of integrator for the sine function.
38       */
39      public void testSinFunction() throws MathException {
40          UnivariateRealFunction f = new SinFunction();
41          UnivariateRealIntegrator integrator = new SimpsonIntegrator();
42          double min, max, expected, result, tolerance;
43  
44          min = 0; max = Math.PI; expected = 2;
45          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
46          result = integrator.integrate(f, min, max);
47          assertEquals(expected, result, tolerance);
48  
49          min = -Math.PI/3; max = 0; expected = -0.5;
50          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
51          result = integrator.integrate(f, min, max);
52          assertEquals(expected, result, tolerance);
53      }
54  
55      /**
56       * Test of integrator for the quintic function.
57       */
58      public void testQuinticFunction() throws MathException {
59          UnivariateRealFunction f = new QuinticFunction();
60          UnivariateRealIntegrator integrator = new SimpsonIntegrator();
61          double min, max, expected, result, tolerance;
62  
63          min = 0; max = 1; expected = -1.0/48;
64          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
65          result = integrator.integrate(f, min, max);
66          assertEquals(expected, result, tolerance);
67  
68          min = 0; max = 0.5; expected = 11.0/768;
69          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
70          result = integrator.integrate(f, min, max);
71          assertEquals(expected, result, tolerance);
72  
73          min = -1; max = 4; expected = 2048/3.0 - 78 + 1.0/48;
74          tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
75          result = integrator.integrate(f, min, max);
76          assertEquals(expected, result, tolerance);
77      }
78  
79      /**
80       * Test of parameters for the integrator.
81       */
82      public void testParameters() throws Exception {
83          UnivariateRealFunction f = new SinFunction();
84          UnivariateRealIntegrator integrator = new SimpsonIntegrator();
85  
86          try {
87              // bad interval
88              integrator.integrate(f, 1, -1);
89              fail("Expecting IllegalArgumentException - bad interval");
90          } catch (IllegalArgumentException ex) {
91              // expected
92          }
93          try {
94              // bad iteration limits
95              integrator.setMinimalIterationCount(5);
96              integrator.setMaximalIterationCount(4);
97              integrator.integrate(f, -1, 1);
98              fail("Expecting IllegalArgumentException - bad iteration limits");
99          } catch (IllegalArgumentException ex) {
100             // expected
101         }
102         try {
103             // bad iteration limits
104             integrator.setMinimalIterationCount(10);
105             integrator.setMaximalIterationCount(99);
106             integrator.integrate(f, -1, 1);
107             fail("Expecting IllegalArgumentException - bad iteration limits");
108         } catch (IllegalArgumentException ex) {
109             // expected
110         }
111     }
112 }