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 3/8 fourth order Runge-Kutta
023 * integrator for Ordinary Differential Equations.
024 *
025 * <p>This method is an explicit Runge-Kutta method, its Butcher-array
026 * is the following one :
027 * <pre>
028 * 0 | 0 0 0 0
029 * 1/3 | 1/3 0 0 0
030 * 2/3 |-1/3 1 0 0
031 * 1 | 1 -1 1 0
032 * |--------------------
033 * | 1/8 3/8 3/8 1/8
034 * </pre>
035 * </p>
036 *
037 * @see EulerIntegrator
038 * @see ClassicalRungeKuttaIntegrator
039 * @see GillIntegrator
040 * @see MidpointIntegrator
041 * @version $Revision: 810196 $ $Date: 2009-09-01 21:47:46 +0200 (mar. 01 sept. 2009) $
042 * @since 1.2
043 */
044
045 public class ThreeEighthesIntegrator extends RungeKuttaIntegrator {
046
047 /** Time steps Butcher array. */
048 private static final double[] STATIC_C = {
049 1.0 / 3.0, 2.0 / 3.0, 1.0
050 };
051
052 /** Internal weights Butcher array. */
053 private static final double[][] STATIC_A = {
054 { 1.0 / 3.0 },
055 { -1.0 / 3.0, 1.0 },
056 { 1.0, -1.0, 1.0 }
057 };
058
059 /** Propagation weights Butcher array. */
060 private static final double[] STATIC_B = {
061 1.0 / 8.0, 3.0 / 8.0, 3.0 / 8.0, 1.0 / 8.0
062 };
063
064 /** Simple constructor.
065 * Build a 3/8 integrator with the given step.
066 * @param step integration step
067 */
068 public ThreeEighthesIntegrator(final double step) {
069 super("3/8", STATIC_C, STATIC_A, STATIC_B, new ThreeEighthesStepInterpolator(), step);
070 }
071
072 }