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 018package org.apache.commons.math4.legacy.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 * 037 * @see EulerIntegrator 038 * @see GillIntegrator 039 * @see MidpointIntegrator 040 * @see ThreeEighthesIntegrator 041 * @see LutherIntegrator 042 * @since 1.2 043 */ 044 045public class ClassicalRungeKuttaIntegrator extends RungeKuttaIntegrator { 046 047 /** Time steps Butcher array. */ 048 private static final double[] STATIC_C = { 049 1.0 / 2.0, 1.0 / 2.0, 1.0 050 }; 051 052 /** Internal weights Butcher array. */ 053 private static final double[][] STATIC_A = { 054 { 1.0 / 2.0 }, 055 { 0.0, 1.0 / 2.0 }, 056 { 0.0, 0.0, 1.0 } 057 }; 058 059 /** Propagation weights Butcher array. */ 060 private static final double[] STATIC_B = { 061 1.0 / 6.0, 1.0 / 3.0, 1.0 / 3.0, 1.0 / 6.0 062 }; 063 064 /** Simple constructor. 065 * Build a fourth-order Runge-Kutta integrator with the given 066 * step. 067 * @param step integration step 068 */ 069 public ClassicalRungeKuttaIntegrator(final double step) { 070 super("classical Runge-Kutta", STATIC_C, STATIC_A, STATIC_B, 071 new ClassicalRungeKuttaStepInterpolator(), step); 072 } 073}