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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.sampling;
19  
20  import java.io.IOException;
21  import java.io.ObjectInput;
22  import java.io.ObjectOutput;
23  
24  import org.apache.commons.math.ode.DerivativeException;
25  import org.apache.commons.math.ode.nonstiff.EmbeddedRungeKuttaIntegrator;
26  
27  /** This class is a step interpolator that does nothing.
28   *
29   * <p>This class is used when the {@link StepHandler "step handler"}
30   * set up by the user does not need step interpolation. It does not
31   * recompute the state when {@link AbstractStepInterpolator#setInterpolatedTime
32   * setInterpolatedTime} is called. This implies the interpolated state
33   * is always the state at the end of the current step.</p>
34   *
35   * @see StepHandler
36   *
37   * @version $Revision: 782431 $ $Date: 2009-06-07 15:04:37 -0400 (Sun, 07 Jun 2009) $
38   * @since 1.2
39   */
40  
41  public class DummyStepInterpolator
42    extends AbstractStepInterpolator {
43  
44    /** Simple constructor.
45     * This constructor builds an instance that is not usable yet, the
46     * <code>AbstractStepInterpolator.reinitialize</code> protected method
47     * should be called before using the instance in order to initialize
48     * the internal arrays. This constructor is used only in order to delay
49     * the initialization in some cases. As an example, the {@link
50     * EmbeddedRungeKuttaIntegrator} uses the prototyping design pattern
51     * to create the step interpolators by cloning an uninitialized
52     * model and latter initializing the copy.
53     */
54    public DummyStepInterpolator() {
55      super();
56    }
57  
58    /** Simple constructor.
59     * @param y reference to the integrator array holding the state at
60     * the end of the step
61     * @param forward integration direction indicator
62     */
63    public DummyStepInterpolator(final double[] y, final boolean forward) {
64      super(y, forward);
65    }
66  
67    /** Copy constructor.
68     * @param interpolator interpolator to copy from. The copy is a deep
69     * copy: its arrays are separated from the original arrays of the
70     * instance
71     */
72    public DummyStepInterpolator(final DummyStepInterpolator interpolator) {
73      super(interpolator);
74    }
75  
76    /** Really copy the finalized instance.
77     * @return a copy of the finalized instance
78     */
79    @Override
80    protected StepInterpolator doCopy() {
81      return new DummyStepInterpolator(this);
82    }
83  
84    /** Compute the state at the interpolated time.
85     * In this class, this method does nothing: the interpolated state
86     * is always the state at the end of the current step.
87     * @param theta normalized interpolation abscissa within the step
88     * (theta is zero at the previous time step and one at the current time step)
89     * @param oneMinusThetaH time gap between the interpolated time and
90     * the current time
91     * @throws DerivativeException this exception is propagated to the caller if the
92     * underlying user function triggers one
93     */
94    @Override
95    protected void computeInterpolatedStateAndDerivatives(final double theta, final double oneMinusThetaH)
96      throws DerivativeException {
97        System.arraycopy(currentState, 0, interpolatedState, 0, currentState.length);
98    }
99      
100   /** Write the instance to an output channel.
101    * @param out output channel
102    * @exception IOException if the instance cannot be written
103    */
104   @Override
105   public void writeExternal(final ObjectOutput out)
106     throws IOException {
107     // save the state of the base class
108     writeBaseExternal(out);
109   }
110 
111   /** Read the instance from an input channel.
112    * @param in input channel
113    * @exception IOException if the instance cannot be read
114    */
115   @Override
116   public void readExternal(final ObjectInput in)
117     throws IOException {
118 
119     // read the base class 
120     final double t = readBaseExternal(in);
121 
122     // we can now set the interpolated time and state
123     setInterpolatedTime(t);
124 
125   }
126 
127   /** Serializable version identifier */
128   private static final long serialVersionUID = 1708010296707839488L;
129 
130 }