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 import java.io.ObjectInput;
21 import java.io.ObjectOutput;
22 import java.io.IOException;
23
24 /** This class is a step interpolator that does nothing.
25 *
26 * <p>This class is used when the {@link StepHandler "step handler"}
27 * set up by the user does not need step interpolation. It does not
28 * recompute the state when {@link AbstractStepInterpolator#setInterpolatedTime
29 * setInterpolatedTime} is called. This implies the interpolated state
30 * is always the state at the end of the current step.</p>
31 *
32 * @see StepHandler
33 *
34 * @version $Revision: 620312 $ $Date: 2008-02-10 12:28:59 -0700 (Sun, 10 Feb 2008) $
35 * @since 1.2
36 */
37
38 public class DummyStepInterpolator
39 extends AbstractStepInterpolator {
40
41 /** Simple constructor.
42 * This constructor builds an instance that is not usable yet, the
43 * <code>AbstractStepInterpolator.reinitialize</code> protected method
44 * should be called before using the instance in order to initialize
45 * the internal arrays. This constructor is used only in order to delay
46 * the initialization in some cases. As an example, the {@link
47 * EmbeddedRungeKuttaIntegrator} uses the prototyping design pattern
48 * to create the step interpolators by cloning an uninitialized
49 * model and latter initializing the copy.
50 */
51 public DummyStepInterpolator() {
52 super();
53 }
54
55 /** Simple constructor.
56 * @param y reference to the integrator array holding the state at
57 * the end of the step
58 * @param forward integration direction indicator
59 */
60 protected DummyStepInterpolator(double[] y, boolean forward) {
61 super(y, forward);
62 }
63
64 /** Copy constructor.
65 * @param interpolator interpolator to copy from. The copy is a deep
66 * copy: its arrays are separated from the original arrays of the
67 * instance
68 */
69 public DummyStepInterpolator(DummyStepInterpolator interpolator) {
70 super(interpolator);
71 }
72
73 /** Really copy the finalized instance.
74 * @return a copy of the finalized instance
75 */
76 protected StepInterpolator doCopy() {
77 return new DummyStepInterpolator(this);
78 }
79
80 /** Compute the state at the interpolated time.
81 * In this class, this method does nothing: the interpolated state
82 * is always the state at the end of the current step.
83 * @param theta normalized interpolation abscissa within the step
84 * (theta is zero at the previous time step and one at the current time step)
85 * @param oneMinusThetaH time gap between the interpolated time and
86 * the current time
87 * @throws DerivativeException this exception is propagated to the caller if the
88 * underlying user function triggers one
89 */
90 protected void computeInterpolatedState(double theta, double oneMinusThetaH)
91 throws DerivativeException {
92 System.arraycopy(currentState, 0, interpolatedState, 0, currentState.length);
93 }
94
95 /** Write the instance to an output channel.
96 * @param out output channel
97 * @exception IOException if the instance cannot be written
98 */
99 public void writeExternal(ObjectOutput out)
100 throws IOException {
101 // save the state of the base class
102 writeBaseExternal(out);
103 }
104
105 /** Read the instance from an input channel.
106 * @param in input channel
107 * @exception IOException if the instance cannot be read
108 */
109 public void readExternal(ObjectInput in)
110 throws IOException {
111
112 // read the base class
113 double t = readBaseExternal(in);
114
115 try {
116 // we can now set the interpolated time and state
117 setInterpolatedTime(t);
118 } catch (DerivativeException e) {
119 throw new IOException(e.getMessage());
120 }
121
122 }
123
124 /** Serializable version identifier */
125 private static final long serialVersionUID = 1708010296707839488L;
126
127 }