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1   /*
2    * @(#) Adams.java Apr 21, 2004
3    * 
4    * Copyright (c) 2003 Delft University of Technology Jaffalaan 5, 2628 BX Delft,
5    * the Netherlands All rights reserved.
6    * 
7    * This software is proprietary information of Delft University of Technology
8    * The code is published under the General Public License
9    */
10  package nl.tudelft.simulation.jstats.ode.integrators;
11  
12  import nl.tudelft.simulation.jstats.ode.DifferentialEquationInterface;
13  
14  /***
15   * The Milne numerical estimator as described in <a
16   * href="http://mathworld.wolfram.com/MilnesMethod.html">
17   * http://mathworld.wolfram.com/MilnesMethod.html </a>
18   * <p>
19   * (c) copyright 2003 <a href="http://www.simulation.tudelft.nl">Delft
20   * University of Technology </a>, the Netherlands. <br>
21   * See for project information <a
22   * href="http://www.simulation.tudelft.nl">www.simulation.tudelft.nl </a> <br>
23   * License of use: <a href="http://www.gnu.org/copyleft/gpl.html">General Public
24   * License (GPL) </a>, no warranty <br>
25   * 
26   * @author <a href="http://www.tbm.tudelft.nl/webstaf/peterja/index.htm">Peter
27   *         Jacobs </a>
28   * @version 1.2 Apr 21, 2004
29   * @since 1.4
30   */
31  public class Milne extends CachingNumericalIntegrator
32  {
33  	/***
34  	 * constructs a new Milne integrator
35  	 * 
36  	 * @param timeStep the timeStep to use in the estimation.
37  	 * @param equation the equation to use.
38  	 */
39  	public Milne(final double timeStep,
40  			final DifferentialEquationInterface equation)
41  	{
42  		super(timeStep, equation, 4, NumericalIntegrator.RUNGEKUTTA4, 10);
43  	}
44  
45  	/***
46  	 * constructs a new Milne integrator, indicating the starting method and
47  	 * number of substeps
48  	 * 
49  	 * @param timeStep the timeStep to use in the estimation.
50  	 * @param equation the equation to use.
51  	 * @param integrationMethod the primer integrator to use
52  	 * @param startingSubSteps the number of substeps per timestep during
53  	 *        starting of the integrator
54  	 */
55  	public Milne(final double timeStep,
56  			final DifferentialEquationInterface equation,
57  			final short integrationMethod, final int startingSubSteps)
58  	{
59  		super(timeStep, equation, 4, integrationMethod, startingSubSteps);
60  	}
61  
62  	/***
63  	 * @see nl.tudelft.simulation.jstats.ode.integrators.CachingNumericalIntegrator#next(double)
64  	 */
65  	public double[] next(final double x)
66  	{
67  		double[] y3 = super.getY(3);
68  		double[] y1 = super.getY(1);
69  		double[] dy2 = super.getDY(2);
70  		double[] dy1 = super.getDY(1);
71  		double[] dy0 = super.getDY(0);
72  
73  		//Let's evaluate the predictor
74  		double[] p = super.add(y3, super.multiply(4 * this.timeStep / 3.0,
75  				super.add(super.multiply(2.0, dy0), super.multiply(-1.0, dy1),
76  						super.multiply(2.0, dy2))));
77  
78  		//Now we compute the corrector
79  		return super.add(y1, super.multiply(this.timeStep / 3.0, super.add(
80  				super.multiply(1.0, dy1), super.multiply(4.0, dy0),
81  				this.equation.dy(x + this.timeStep, p))));
82  	}
83  }