001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.math.ode.nonstiff;
019
020
021 /**
022 * This class implements the classical fourth order Runge-Kutta
023 * integrator for Ordinary Differential Equations (it is the most
024 * often used Runge-Kutta method).
025 *
026 * <p>This method is an explicit Runge-Kutta method, its Butcher-array
027 * is the following one :
028 * <pre>
029 * 0 | 0 0 0 0
030 * 1/2 | 1/2 0 0 0
031 * 1/2 | 0 1/2 0 0
032 * 1 | 0 0 1 0
033 * |--------------------
034 * | 1/6 1/3 1/3 1/6
035 * </pre>
036 * </p>
037 *
038 * @see EulerIntegrator
039 * @see GillIntegrator
040 * @see MidpointIntegrator
041 * @see ThreeEighthesIntegrator
042 * @version $Revision: 810196 $ $Date: 2009-09-01 21:47:46 +0200 (mar. 01 sept. 2009) $
043 * @since 1.2
044 */
045
046 public class ClassicalRungeKuttaIntegrator extends RungeKuttaIntegrator {
047
048 /** Time steps Butcher array. */
049 private static final double[] STATIC_C = {
050 1.0 / 2.0, 1.0 / 2.0, 1.0
051 };
052
053 /** Internal weights Butcher array. */
054 private static final double[][] STATIC_A = {
055 { 1.0 / 2.0 },
056 { 0.0, 1.0 / 2.0 },
057 { 0.0, 0.0, 1.0 }
058 };
059
060 /** Propagation weights Butcher array. */
061 private static final double[] STATIC_B = {
062 1.0 / 6.0, 1.0 / 3.0, 1.0 / 3.0, 1.0 / 6.0
063 };
064
065 /** Simple constructor.
066 * Build a fourth-order Runge-Kutta integrator with the given
067 * step.
068 * @param step integration step
069 */
070 public ClassicalRungeKuttaIntegrator(final double step) {
071 super("classical Runge-Kutta", STATIC_C, STATIC_A, STATIC_B,
072 new ClassicalRungeKuttaStepInterpolator(), step);
073 }
074
075 }