/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.analysis.integration;

import org.apache.commons.math.MathException;
import org.apache.commons.math.analysis.QuinticFunction;
import org.apache.commons.math.analysis.SinFunction;
import org.apache.commons.math.analysis.UnivariateRealFunction;

import junit.framework.TestCase;

/**
 * Testcase for Simpson integrator.
 * <p>
 * Test runs show that for a default relative accuracy of 1E-6, it generally
 * takes 5 to 10 iterations for the integral to converge.
 * 
 * @version $Revision$ $Date$
 */
public final class SimpsonIntegratorTest extends TestCase {

	/**
	 * Test of integrator for the sine function.
	 */
	public void testSinFunction() throws MathException {
		UnivariateRealFunction f = new SinFunction();
		UnivariateRealIntegrator integrator = new SimpsonIntegrator();
		double min, max, expected, result, tolerance;

		min = 0;
		max = Math.PI;
		expected = 2;
		tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
		result = integrator.integrate(f, min, max);
		assertEquals(expected, result, tolerance);

		min = -Math.PI / 3;
		max = 0;
		expected = -0.5;
		tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
		result = integrator.integrate(f, min, max);
		assertEquals(expected, result, tolerance);
	}

	/**
	 * Test of integrator for the quintic function.
	 */
	public void testQuinticFunction() throws MathException {
		UnivariateRealFunction f = new QuinticFunction();
		UnivariateRealIntegrator integrator = new SimpsonIntegrator();
		double min, max, expected, result, tolerance;

		min = 0;
		max = 1;
		expected = -1.0 / 48;
		tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
		result = integrator.integrate(f, min, max);
		assertEquals(expected, result, tolerance);

		min = 0;
		max = 0.5;
		expected = 11.0 / 768;
		tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
		result = integrator.integrate(f, min, max);
		assertEquals(expected, result, tolerance);

		min = -1;
		max = 4;
		expected = 2048 / 3.0 - 78 + 1.0 / 48;
		tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
		result = integrator.integrate(f, min, max);
		assertEquals(expected, result, tolerance);
	}

	/**
	 * Test of parameters for the integrator.
	 */
	public void testParameters() throws Exception {
		UnivariateRealFunction f = new SinFunction();
		UnivariateRealIntegrator integrator = new SimpsonIntegrator();

		try {
			// bad interval
			integrator.integrate(f, 1, -1);
			fail("Expecting IllegalArgumentException - bad interval");
		} catch (IllegalArgumentException ex) {
			// expected
		}
		try {
			// bad iteration limits
			integrator.setMinimalIterationCount(5);
			integrator.setMaximalIterationCount(4);
			integrator.integrate(f, -1, 1);
			fail("Expecting IllegalArgumentException - bad iteration limits");
		} catch (IllegalArgumentException ex) {
			// expected
		}
		try {
			// bad iteration limits
			integrator.setMinimalIterationCount(10);
			integrator.setMaximalIterationCount(99);
			integrator.integrate(f, -1, 1);
			fail("Expecting IllegalArgumentException - bad iteration limits");
		} catch (IllegalArgumentException ex) {
			// expected
		}
	}
}
