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.math4.legacy.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 /** theoretical state */
39 private double[] y;
40
41 /**
42 * Simple constructor.
43 */
44 public TestProblem6() {
45 super();
46 double[] y0 = { -360.0 };
47 setInitialConditions(0.0, y0);
48 setFinalConditions(1.0);
49 double[] errorScale = { 1.0 };
50 setErrorScale(errorScale);
51 y = new double[y0.length];
52 }
53
54 @Override
55 public void doComputeDerivatives(double t, double[] y, double[] yDot) {
56
57 // compute the derivatives
58 double t2 = t * t;
59 double t4 = t2 * t2;
60 double t5 = t4 * t;
61 for (int i = 0; i < getDimension(); ++i) {
62 yDot[i] = 3 * t5 - y[i];
63 }
64 }
65
66 @Override
67 public double[] computeTheoreticalState(double t) {
68 for (int i = 0; i < getDimension(); ++i) {
69 y[i] = ((((3 * t - 15) * t + 60) * t - 180) * t + 360) * t - 360;
70 }
71 return y;
72 }
73 }