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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  /** This interface represents a first order differential equations set.
21   *
22   * <p>This interface should be implemented by all real first order
23   * differential equation problems before they can be handled by the
24   * integrators {@link FirstOrderIntegrator#integrate} method.</p>
25   *
26   * <p>A first order differential equations problem, as seen by an
27   * integrator is the time derivative <code>dY/dt</code> of a state
28   * vector <code>Y</code>, both being one dimensional arrays. From the
29   * integrator point of view, this derivative depends only on the
30   * current time <code>t</code> and on the state vector
31   * <code>Y</code>.</p>
32   *
33   * <p>For real problems, the derivative depends also on parameters
34   * that do not belong to the state vector (dynamical model constants
35   * for example). These constants are completely outside of the scope
36   * of this interface, the classes that implement it are allowed to
37   * handle them as they want.</p>
38   *
39   * @see FirstOrderIntegrator
40   * @see FirstOrderConverter
41   * @see SecondOrderDifferentialEquations
42   *
43   * @version $Revision: 620312 $ $Date: 2008-02-10 12:28:59 -0700 (Sun, 10 Feb 2008) $
44   * @since 1.2
45   */
46  
47  public interface FirstOrderDifferentialEquations {
48      
49      /** Get the dimension of the problem.
50       * @return dimension of the problem
51       */
52      public 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 placeholder array where to put the time derivative of the state vector
58       * @throws DerivativeException this exception is propagated to the caller if the
59       * underlying user function triggers one
60       */
61      public void computeDerivatives(double t, double[] y, double[] yDot)
62      throws DerivativeException;
63      
64  }