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