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 */
17package org.apache.commons.math.ode;
18
19
20/** This interface represents a first order differential equations set
21 * with a main set of equations and an extension set.
22 *
23 * <p>
24 * This interface is a simple extension on the {@link
25 * FirstOrderDifferentialEquations} that allows to identify which part
26 * of a complete set of differential equations correspond to the main
27 * set and which part correspond to the extension set.
28 * </p>
29 * <p>
30 * One typical use case is the computation of Jacobians. The main
31 * set of equations correspond to the raw ode, and we add to this set
32 * another bunch of equations which represent the jacobians of the
33 * main set. In that case, we want the integrator to use <em>only</em>
34 * the main set to estimate the errors and hence the step sizes. It should
35 * <em>not</em> use the additional equations in this computation. If the
36 * complete ode implements this interface, the {@link FirstOrderIntegrator
37 * integrator} will be able to know where the main set ends and where the
38 * extended set begins.
39 * </p>
40 * <p>
41 * We consider that the main set always corresponds to the first equations
42 * and the extended set to the last equations.
43 * </p>
44 *
45 * @see FirstOrderDifferentialEquations
46 *
47 * @version $Revision: 980981 $ $Date: 2010-07-31 00:03:04 +0200 (sam. 31 juil. 2010) $
48 * @since 2.2
49 */
50
51public interface ExtendedFirstOrderDifferentialEquations extends FirstOrderDifferentialEquations {
52
53    /** Return the dimension of the main set of equations.
54     * <p>
55     * The main set of equations represent the first part of an ODE state.
56     * The error estimations and adaptive step size computation should be
57     * done on this first part only, not on the final part of the state
58     * which represent an extension set of equations which are considered
59     * secondary.
60     * </p>
61     * @return dimension of the main set of equations, must be lesser than or
62     * equal to the {@link #getDimension() total dimension}
63     */
64    int getMainSetDimension();
65
66}
67