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 18 package org.apache.commons.math.ode.nonstiff; 19 20 21 /** 22 * This class implements a second order Runge-Kutta integrator for 23 * 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 29 * 1/2 | 1/2 0 30 * |---------- 31 * | 0 1 32 * </pre> 33 * </p> 34 * 35 * @see EulerIntegrator 36 * @see ClassicalRungeKuttaIntegrator 37 * @see GillIntegrator 38 * 39 * @version $Revision: 810196 $ $Date: 2009-09-01 21:47:46 +0200 (mar. 01 sept. 2009) $ 40 * @since 1.2 41 */ 42 43 public class MidpointIntegrator extends RungeKuttaIntegrator { 44 45 /** Time steps Butcher array. */ 46 private static final double[] STATIC_C = { 47 1.0 / 2.0 48 }; 49 50 /** Internal weights Butcher array. */ 51 private static final double[][] STATIC_A = { 52 { 1.0 / 2.0 } 53 }; 54 55 /** Propagation weights Butcher array. */ 56 private static final double[] STATIC_B = { 57 0.0, 1.0 58 }; 59 60 /** Simple constructor. 61 * Build a midpoint integrator with the given step. 62 * @param step integration step 63 */ 64 public MidpointIntegrator(final double step) { 65 super("midpoint", STATIC_C, STATIC_A, STATIC_B, new MidpointStepInterpolator(), step); 66 } 67 68 } 69
