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 18 package org.apache.commons.math.ode; 19 20 /** 21 * This class is used in the junit tests for the ODE integrators. 22 23 * <p>This specific problem is the following differential equation : 24 * <pre> 25 * y' = 3x^5 - y 26 * </pre> 27 * when the initial condition is y(0) = -360, the solution of this 28 * equation degenerates to a simple quintic polynomial function : 29 * <pre> 30 * y (t) = 3x^5 - 15x^4 + 60x^3 - 180x^2 + 360x - 360 31 * </pre> 32 * </p> 33 34 */ 35 public class TestProblem6 36 extends TestProblemAbstract { 37 38 /** Serializable version identifier. */ 39 private static final long serialVersionUID = 1353409119804352378L; 40 41 /** theoretical state */ 42 private double[] y; 43 44 /** 45 * Simple constructor. 46 */ 47 public TestProblem6() { 48 super(); 49 double[] y0 = { -360.0 }; 50 setInitialConditions(0.0, y0); 51 setFinalConditions(1.0); 52 double[] errorScale = { 1.0 }; 53 setErrorScale(errorScale); 54 y = new double[y0.length]; 55 } 56 57 /** 58 * Copy constructor. 59 * @param problem problem to copy 60 */ 61 public TestProblem6(TestProblem6 problem) { 62 super(problem); 63 y = problem.y.clone(); 64 } 65 66 /** {@inheritDoc} */ 67 public TestProblem6 copy() { 68 return new TestProblem6(this); 69 } 70 71 @Override 72 public void doComputeDerivatives(double t, double[] y, double[] yDot) { 73 74 // compute the derivatives 75 double t2 = t * t; 76 double t4 = t2 * t2; 77 double t5 = t4 * t; 78 for (int i = 0; i < n; ++i) { 79 yDot[i] = 3 * t5 - y[i]; 80 } 81 82 } 83 84 @Override 85 public double[] computeTheoreticalState(double t) { 86 for (int i = 0; i < n; ++i) { 87 y[i] = ((((3 * t - 15) * t + 60) * t - 180) * t + 360) * t - 360; 88 } 89 return y; 90 } 91 92 }