001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.math.analysis.integration;
018    
019    import org.apache.commons.math.MathException;
020    import org.apache.commons.math.analysis.QuinticFunction;
021    import org.apache.commons.math.analysis.SinFunction;
022    import org.apache.commons.math.analysis.UnivariateRealFunction;
023    
024    import junit.framework.TestCase;
025    
026    /**
027     * Testcase for Romberg integrator.
028     * <p>
029     * Romberg algorithm is very fast for good behavior integrand. Test runs
030     * show that for a default relative accuracy of 1E-6, it generally takes
031     * takes less than 5 iterations for the integral to converge.
032     * 
033     * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $ 
034     */
035    public final class RombergIntegratorTest extends TestCase {
036    
037        /**
038         * Test of integrator for the sine function.
039         */
040        public void testSinFunction() throws MathException {
041            UnivariateRealFunction f = new SinFunction();
042            UnivariateRealIntegrator integrator = new RombergIntegrator();
043            double min, max, expected, result, tolerance;
044    
045            min = 0; max = Math.PI; expected = 2;
046            tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
047            result = integrator.integrate(f, min, max);
048            assertEquals(expected, result, tolerance);
049    
050            min = -Math.PI/3; max = 0; expected = -0.5;
051            tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
052            result = integrator.integrate(f, min, max);
053            assertEquals(expected, result, tolerance);
054        }
055    
056        /**
057         * Test of integrator for the quintic function.
058         */
059        public void testQuinticFunction() throws MathException {
060            UnivariateRealFunction f = new QuinticFunction();
061            UnivariateRealIntegrator integrator = new RombergIntegrator();
062            double min, max, expected, result, tolerance;
063    
064            min = 0; max = 1; expected = -1.0/48;
065            tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
066            result = integrator.integrate(f, min, max);
067            assertEquals(expected, result, tolerance);
068    
069            min = 0; max = 0.5; expected = 11.0/768;
070            tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
071            result = integrator.integrate(f, min, max);
072            assertEquals(expected, result, tolerance);
073    
074            min = -1; max = 4; expected = 2048/3.0 - 78 + 1.0/48;
075            tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
076            result = integrator.integrate(f, min, max);
077            assertEquals(expected, result, tolerance);
078        }
079    
080        /**
081         * Test of parameters for the integrator.
082         */
083        public void testParameters() throws Exception {
084            UnivariateRealFunction f = new SinFunction();
085            UnivariateRealIntegrator integrator = new RombergIntegrator();
086    
087            try {
088                // bad interval
089                integrator.integrate(f, 1, -1);
090                fail("Expecting IllegalArgumentException - bad interval");
091            } catch (IllegalArgumentException ex) {
092                // expected
093            }
094            try {
095                // bad iteration limits
096                integrator.setMinimalIterationCount(5);
097                integrator.setMaximalIterationCount(4);
098                integrator.integrate(f, -1, 1);
099                fail("Expecting IllegalArgumentException - bad iteration limits");
100            } catch (IllegalArgumentException ex) {
101                // expected
102            }
103            try {
104                // bad iteration limits
105                integrator.setMinimalIterationCount(10);
106                integrator.setMaximalIterationCount(50);
107                integrator.integrate(f, -1, 1);
108                fail("Expecting IllegalArgumentException - bad iteration limits");
109            } catch (IllegalArgumentException ex) {
110                // expected
111            }
112        }
113    }