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 3/8 fourth order Runge-Kutta
23 * integrator for Ordinary Differential Equations.
24 *
25 * <p>This method is an explicit Runge-Kutta method, its Butcher-array
26 * is the following one :
27 * <pre>
28 *    0  |  0    0    0    0
29 *   1/3 | 1/3   0    0    0
30 *   2/3 |-1/3   1    0    0
31 *    1  |  1   -1    1    0
32 *       |--------------------
33 *       | 1/8  3/8  3/8  1/8
34 * </pre>
35 * </p>
36 *
37 * @see EulerIntegrator
38 * @see ClassicalRungeKuttaIntegrator
39 * @see GillIntegrator
40 * @see MidpointIntegrator
41 * @version $Revision: 810196 $ $Date: 2009-09-01 21:47:46 +0200 (mar. 01 sept. 2009) $
42 * @since 1.2
43 */
44
45public class ThreeEighthesIntegrator extends RungeKuttaIntegrator {
46
47  /** Time steps Butcher array. */
48  private static final double[] STATIC_C = {
49    1.0 / 3.0, 2.0 / 3.0, 1.0
50  };
51
52  /** Internal weights Butcher array. */
53  private static final double[][] STATIC_A = {
54    {  1.0 / 3.0 },
55    { -1.0 / 3.0, 1.0 },
56    {  1.0, -1.0, 1.0 }
57  };
58
59  /** Propagation weights Butcher array. */
60  private static final double[] STATIC_B = {
61    1.0 / 8.0, 3.0 / 8.0, 3.0 / 8.0, 1.0 / 8.0
62  };
63
64  /** Simple constructor.
65   * Build a 3/8 integrator with the given step.
66   * @param step integration step
67   */
68  public ThreeEighthesIntegrator(final double step) {
69    super("3/8", STATIC_C, STATIC_A, STATIC_B, new ThreeEighthesStepInterpolator(), step);
70  }
71
72}
73