View Javadoc

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 }