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.math3.ode.nonstiff;
019
020
021/**
022 * This class implements a second order Runge-Kutta integrator for
023 * 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
029 *   1/2 | 1/2   0
030 *       |----------
031 *       |  0    1
032 * </pre>
033 * </p>
034 *
035 * @see EulerIntegrator
036 * @see ClassicalRungeKuttaIntegrator
037 * @see GillIntegrator
038 * @see ThreeEighthesIntegrator
039 * @see LutherIntegrator
040 *
041 * @version $Id: MidpointIntegrator.java 1588755 2014-04-20 13:30:16Z luc $
042 * @since 1.2
043 */
044
045public class MidpointIntegrator extends RungeKuttaIntegrator {
046
047  /** Time steps Butcher array. */
048  private static final double[] STATIC_C = {
049    1.0 / 2.0
050  };
051
052  /** Internal weights Butcher array. */
053  private static final double[][] STATIC_A = {
054    { 1.0 / 2.0 }
055  };
056
057  /** Propagation weights Butcher array. */
058  private static final double[] STATIC_B = {
059    0.0, 1.0
060  };
061
062  /** Simple constructor.
063   * Build a midpoint integrator with the given step.
064   * @param step integration step
065   */
066  public MidpointIntegrator(final double step) {
067    super("midpoint", STATIC_C, STATIC_A, STATIC_B, new MidpointStepInterpolator(), step);
068  }
069
070}