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 * https://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 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22
23 package org.hipparchus.ode;
24
25 import org.hipparchus.Field;
26 import org.hipparchus.CalculusFieldElement;
27 import org.hipparchus.util.MathArrays;
28
29 /**
30 * This class is used in the junit tests for the ODE integrators.
31
32 * <p>This specific problem is the following differential equation :
33 * <pre>
34 * y' = 3x^5 - y
35 * </pre>
36 * when the initial condition is y(0) = -360, the solution of this
37 * equation degenerates to a simple quintic polynomial function :
38 * <pre>
39 * y (t) = 3x^5 - 15x^4 + 60x^3 - 180x^2 + 360x - 360
40 * </pre>
41 * </p>
42
43 * @param <T> the type of the field elements
44 */
45 public class TestFieldProblem6<T extends CalculusFieldElement<T>>
46 extends TestFieldProblemAbstract<T> {
47
48 /**
49 * Simple constructor.
50 * @param field field to which elements belong
51 */
52 public TestFieldProblem6(Field<T> field) {
53 super(convert(field, 0.0),
54 convert(field, new double[] { -360.0 }),
55 convert(field, 1.0),
56 convert(field, new double[] { 1.0 }));
57 }
58
59 @Override
60 public T[] doComputeDerivatives(T t, T[] y) {
61
62 final T[] yDot = MathArrays.buildArray(getField(), getDimension());
63
64 // compute the derivatives
65 T t2 = t.multiply(t);
66 T t4 = t2.multiply(t2);
67 T t5 = t4.multiply(t);
68 for (int i = 0; i < getDimension(); ++i) {
69 yDot[i] = t5.multiply(3).subtract(y[i]);
70 }
71
72 return yDot;
73
74 }
75
76 @Override
77 public T[] computeTheoreticalState(T t) {
78
79 final T[] y = MathArrays.buildArray(getField(), getDimension());
80
81 for (int i = 0; i < getDimension(); ++i) {
82 y[i] = t.multiply(3).subtract(15).multiply(t).add(60).multiply(t).subtract(180).multiply(t).add(360).multiply(t).subtract(360);
83 }
84
85 return y;
86
87 }
88
89 }