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
18package org.apache.commons.math.ode.nonstiff;
19
20
21/**
22 * This class implements the classical fourth order Runge-Kutta
23 * integrator for Ordinary Differential Equations (it is the most
24 * often used Runge-Kutta method).
25 *
26 * <p>This method is an explicit Runge-Kutta method, its Butcher-array
27 * is the following one :
28 * <pre>
29 *    0  |  0    0    0    0
30 *   1/2 | 1/2   0    0    0
31 *   1/2 |  0   1/2   0    0
32 *    1  |  0    0    1    0
33 *       |--------------------
34 *       | 1/6  1/3  1/3  1/6
35 * </pre>
36 * </p>
37 *
38 * @see EulerIntegrator
39 * @see GillIntegrator
40 * @see MidpointIntegrator
41 * @see ThreeEighthesIntegrator
42 * @version $Revision: 810196 $ $Date: 2009-09-01 21:47:46 +0200 (mar. 01 sept. 2009) $
43 * @since 1.2
44 */
45
46public class ClassicalRungeKuttaIntegrator extends RungeKuttaIntegrator {
47
48  /** Time steps Butcher array. */
49  private static final double[] STATIC_C = {
50    1.0 / 2.0, 1.0 / 2.0, 1.0
51  };
52
53  /** Internal weights Butcher array. */
54  private static final double[][] STATIC_A = {
55    { 1.0 / 2.0 },
56    { 0.0, 1.0 / 2.0 },
57    { 0.0, 0.0, 1.0 }
58  };
59
60  /** Propagation weights Butcher array. */
61  private static final double[] STATIC_B = {
62    1.0 / 6.0, 1.0 / 3.0, 1.0 / 3.0, 1.0 / 6.0
63  };
64
65  /** Simple constructor.
66   * Build a fourth-order Runge-Kutta integrator with the given
67   * step.
68   * @param step integration step
69   */
70  public ClassicalRungeKuttaIntegrator(final double step) {
71    super("classical Runge-Kutta", STATIC_C, STATIC_A, STATIC_B,
72          new ClassicalRungeKuttaStepInterpolator(), step);
73  }
74
75}
76