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 interface represents a second order differential equations set.
22
23 * <p>This interface should be implemented by all real second order
24 * differential equation problems before they can be handled by the
25 * integrators {@link SecondOrderIntegrator#integrate} method.</p>
26 *
27 * <p>A second order differential equations problem, as seen by an
28 * integrator is the second time derivative <code>d2Y/dt^2</code> of a
29 * state vector <code>Y</code>, both being one dimensional
30 * arrays. From the integrator point of view, this derivative depends
31 * only on the current time <code>t</code>, on the state vector
32 * <code>Y</code> and on the first time derivative of the state
33 * vector.</p>
34 *
35 * <p>For real problems, the derivative depends also on parameters
36 * that do not belong to the state vector (dynamical model constants
37 * for example). These constants are completely outside of the scope
38 * of this interface, the classes that implement it are allowed to
39 * handle them as they want.</p>
40 *
41 * @see SecondOrderIntegrator
42 * @see FirstOrderConverter
43 * @see FirstOrderDifferentialEquations
44 * @since 1.2
45 */
46
47 public interface SecondOrderDifferentialEquations {
48
49 /** Get the dimension of the problem.
50 * @return dimension of the problem
51 */
52 int getDimension();
53
54 /** Get the current time derivative of the state vector.
55 * @param t current value of the independent <I>time</I> variable
56 * @param y array containing the current value of the state vector
57 * @param yDot array containing the current value of the first derivative
58 * of the state vector
59 * @param yDDot placeholder array where to put the second time derivative
60 * of the state vector
61 */
62 void computeSecondDerivatives(double t, double[] y, double[] yDot, double[] yDDot);
63 }