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;
19
20 /**
21 * This class represents an interpolator over the last step during an
22 * ODE integration for the 5(4) Higham and Hall integrator.
23 *
24 * @see HighamHall54Integrator
25 *
26 * @version $Revision: 620312 $ $Date: 2008-02-10 12:28:59 -0700 (Sun, 10 Feb 2008) $
27 * @since 1.2
28 */
29
30 class HighamHall54StepInterpolator
31 extends RungeKuttaStepInterpolator {
32
33 /** Simple constructor.
34 * This constructor builds an instance that is not usable yet, the
35 * {@link AbstractStepInterpolator#reinitialize} method should be called
36 * before using the instance in order to initialize the internal arrays. This
37 * constructor is used only in order to delay the initialization in
38 * some cases. The {@link EmbeddedRungeKuttaIntegrator} uses the
39 * prototyping design pattern to create the step interpolators by
40 * cloning an uninitialized model and latter initializing the copy.
41 */
42 public HighamHall54StepInterpolator() {
43 super();
44 }
45
46 /** Copy constructor.
47 * @param interpolator interpolator to copy from. The copy is a deep
48 * copy: its arrays are separated from the original arrays of the
49 * instance
50 */
51 public HighamHall54StepInterpolator(HighamHall54StepInterpolator interpolator) {
52 super(interpolator);
53 }
54
55 /** Really copy the finalized instance.
56 * @return a copy of the finalized instance
57 */
58 protected StepInterpolator doCopy() {
59 return new HighamHall54StepInterpolator(this);
60 }
61
62
63 /** Compute the state at the interpolated time.
64 * @param theta normalized interpolation abscissa within the step
65 * (theta is zero at the previous time step and one at the current time step)
66 * @param oneMinusThetaH time gap between the interpolated time and
67 * the current time
68 * @throws DerivativeException this exception is propagated to the caller if the
69 * underlying user function triggers one
70 */
71 protected void computeInterpolatedState(double theta,
72 double oneMinusThetaH)
73 throws DerivativeException {
74
75 double theta2 = theta * theta;
76
77 double b0 = h * (-1.0/12.0 + theta * (1.0 + theta * (-15.0/4.0 + theta * (16.0/3.0 + theta * -5.0/2.0))));
78 double b2 = h * (-27.0/32.0 + theta2 * (459.0/32.0 + theta * (-243.0/8.0 + theta * 135.0/8.0)));
79 double b3 = h * (4.0/3.0 + theta2 * (-22.0 + theta * (152.0/3.0 + theta * -30.0)));
80 double b4 = h * (-125.0/96.0 + theta2 * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0)));
81 double b5 = h * (-5.0/48.0 + theta2 * (-5.0/16.0 + theta * 5.0/12.0));
82
83 for (int i = 0; i < interpolatedState.length; ++i) {
84 interpolatedState[i] = currentState[i] +
85 b0 * yDotK[0][i] + b2 * yDotK[2][i] + b3 * yDotK[3][i] +
86 b4 * yDotK[4][i] + b5 * yDotK[5][i];
87 }
88
89 }
90
91 /** Serializable version identifier */
92 private static final long serialVersionUID = -3583240427587318654L;
93
94 }