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.Externalizable;
21
22 import org.apache.commons.math.ode.DerivativeException;
23 import org.apache.commons.math.ode.FirstOrderIntegrator;
24 import org.apache.commons.math.ode.SecondOrderIntegrator;
25
26 /** This interface represents an interpolator over the last step
27 * during an ODE integration.
28 *
29 * <p>The various ODE integrators provide objects implementing this
30 * interface to the step handlers. These objects are often custom
31 * objects tightly bound to the integrator internal algorithms. The
32 * handlers can use these objects to retrieve the state vector at
33 * intermediate times between the previous and the current grid points
34 * (this feature is often called dense output).</p>
35 * <p>One important thing to note is that the step handlers may be so
36 * tightly bound to the integrators that they often share some internal
37 * state arrays. This imply that one should <em>never</em> use a direct
38 * reference to a step interpolator outside of the step handler, either
39 * for future use or for use in another thread. If such a need arise, the
40 * step interpolator <em>must</em> be copied using the dedicated
41 * {@link #copy()} method.
42 * </p>
43 *
44 * @see FirstOrderIntegrator
45 * @see SecondOrderIntegrator
46 * @see StepHandler
47 * @version $Revision: 782431 $ $Date: 2009-06-07 15:04:37 -0400 (Sun, 07 Jun 2009) $
48 * @since 1.2
49 */
50
51 public interface StepInterpolator
52 extends Externalizable {
53
54 /**
55 * Get the previous grid point time.
56 * @return previous grid point time
57 */
58 public double getPreviousTime();
59
60 /**
61 * Get the current grid point time.
62 * @return current grid point time
63 */
64 public double getCurrentTime();
65
66 /**
67 * Get the time of the interpolated point.
68 * If {@link #setInterpolatedTime} has not been called, it returns
69 * the current grid point time.
70 * @return interpolation point time
71 */
72 public double getInterpolatedTime();
73
74 /**
75 * Set the time of the interpolated point.
76 * <p>Setting the time outside of the current step is now allowed, but
77 * should be used with care since the accuracy of the interpolator will
78 * probably be very poor far from this step. This allowance has been
79 * added to simplify implementation of search algorithms near the
80 * step endpoints.</p>
81 * <p>Setting the time changes the instance internal state. If a
82 * specific state must be preserved, a copy of the instance must be
83 * created using {@link #copy()}.</p>
84 * @param time time of the interpolated point
85 */
86 public void setInterpolatedTime(double time);
87
88 /**
89 * Get the state vector of the interpolated point.
90 * <p>The returned vector is a reference to a reused array, so
91 * it should not be modified and it should be copied if it needs
92 * to be preserved across several calls.</p>
93 * @return state vector at time {@link #getInterpolatedTime}
94 * @see #getInterpolatedDerivatives()
95 * @throws DerivativeException if this call induces an automatic
96 * step finalization that throws one
97 */
98 public double[] getInterpolatedState()
99 throws DerivativeException;
100
101 /**
102 * Get the derivatives of the state vector of the interpolated point.
103 * <p>The returned vector is a reference to a reused array, so
104 * it should not be modified and it should be copied if it needs
105 * to be preserved across several calls.</p>
106 * @return derivatives of the state vector at time {@link #getInterpolatedTime}
107 * @see #getInterpolatedState()
108 * @throws DerivativeException if this call induces an automatic
109 * step finalization that throws one
110 * @since 2.0
111 */
112 public double[] getInterpolatedDerivatives()
113 throws DerivativeException;
114
115 /** Check if the natural integration direction is forward.
116 * <p>This method provides the integration direction as specified by
117 * the integrator itself, it avoid some nasty problems in
118 * degenerated cases like null steps due to cancellation at step
119 * initialization, step control or discrete events
120 * triggering.</p>
121 * @return true if the integration variable (time) increases during
122 * integration
123 */
124 public boolean isForward();
125
126 /** Copy the instance.
127 * <p>The copied instance is guaranteed to be independent from the
128 * original one. Both can be used with different settings for
129 * interpolated time without any side effect.</p>
130 * @return a deep copy of the instance, which can be used independently.
131 * @throws DerivativeException if this call induces an automatic
132 * step finalization that throws one
133 * @see #setInterpolatedTime(double)
134 */
135 public StepInterpolator copy() throws DerivativeException;
136
137 }