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
18package org.apache.commons.math.ode.nonstiff;
19
20import org.apache.commons.math.ode.DerivativeException;
21import org.apache.commons.math.ode.sampling.StepInterpolator;
22
23/**
24 * This class represents an interpolator over the last step during an
25 * ODE integration for the 5(4) Higham and Hall integrator.
26 *
27 * @see HighamHall54Integrator
28 *
29 * @version $Revision: 1073158 $ $Date: 2011-02-21 22:46:52 +0100 (lun. 21 févr. 2011) $
30 * @since 1.2
31 */
32
33class HighamHall54StepInterpolator
34  extends RungeKuttaStepInterpolator {
35
36  /** Serializable version identifier */
37  private static final long serialVersionUID = -3583240427587318654L;
38
39  /** Simple constructor.
40   * This constructor builds an instance that is not usable yet, the
41   * {@link
42   * org.apache.commons.math.ode.sampling.AbstractStepInterpolator#reinitialize}
43   * method should be called before using the instance in order to
44   * initialize the internal arrays. This constructor is used only
45   * in order to delay the initialization in some cases. The {@link
46   * EmbeddedRungeKuttaIntegrator} uses the prototyping design pattern
47   * to create the step interpolators by cloning an uninitialized model
48   * and later initializing the copy.
49   */
50  public HighamHall54StepInterpolator() {
51    super();
52  }
53
54  /** Copy constructor.
55   * @param interpolator interpolator to copy from. The copy is a deep
56   * copy: its arrays are separated from the original arrays of the
57   * instance
58   */
59  public HighamHall54StepInterpolator(final HighamHall54StepInterpolator interpolator) {
60    super(interpolator);
61  }
62
63  /** {@inheritDoc} */
64  @Override
65  protected StepInterpolator doCopy() {
66    return new HighamHall54StepInterpolator(this);
67  }
68
69
70  /** {@inheritDoc} */
71  @Override
72  protected void computeInterpolatedStateAndDerivatives(final double theta,
73                                          final double oneMinusThetaH)
74    throws DerivativeException {
75
76    final double theta2 = theta * theta;
77
78    final 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))));
79    final double b2 = h * (-27.0/32.0 + theta2 * (459.0/32.0 + theta * (-243.0/8.0 + theta * 135.0/8.0)));
80    final double b3 = h * (4.0/3.0 + theta2 * (-22.0 + theta * (152.0/3.0  + theta * -30.0)));
81    final double b4 = h * (-125.0/96.0 + theta2 * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0)));
82    final double b5 = h * (-5.0/48.0 + theta2 * (-5.0/16.0 + theta * 5.0/12.0));
83    final double bDot0 = 1 + theta * (-15.0/2.0 + theta * (16.0 - 10.0 * theta));
84    final double bDot2 = theta * (459.0/16.0 + theta * (-729.0/8.0 + 135.0/2.0 * theta));
85    final double bDot3 = theta * (-44.0 + theta * (152.0 - 120.0 * theta));
86    final double bDot4 = theta * (375.0/16.0 + theta * (-625.0/8.0 + 125.0/2.0 * theta));
87    final double bDot5 = theta * 5.0/8.0 * (2 * theta - 1);
88
89    for (int i = 0; i < interpolatedState.length; ++i) {
90        final double yDot0 = yDotK[0][i];
91        final double yDot2 = yDotK[2][i];
92        final double yDot3 = yDotK[3][i];
93        final double yDot4 = yDotK[4][i];
94        final double yDot5 = yDotK[5][i];
95        interpolatedState[i] =
96            currentState[i] + b0 * yDot0 + b2 * yDot2 + b3 * yDot3 + b4 * yDot4 + b5 * yDot5;
97        interpolatedDerivatives[i] =
98            bDot0 * yDot0 + bDot2 * yDot2 + bDot3 * yDot3 + bDot4 * yDot4 + bDot5 * yDot5;
99    }
100
101  }
102
103}
104