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 * https://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 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22
23 package org.hipparchus.ode.sampling;
24
25 import org.hipparchus.exception.MathIllegalStateException;
26 import org.hipparchus.ode.EquationsMapper;
27 import org.hipparchus.ode.ODEStateAndDerivative;
28 import org.hipparchus.util.FastMath;
29
30 /** This abstract class represents an interpolator over the last step
31 * during an ODE integration.
32 *
33 * <p>The various ODE integrators provide objects extending this class
34 * to the step handlers. The handlers can use these objects to
35 * retrieve the state vector at intermediate times between the
36 * previous and the current grid points (dense output).</p>
37 *
38 * @see org.hipparchus.ode.ODEIntegrator
39 * @see ODEStepHandler
40 */
41
42 public abstract class AbstractODEStateInterpolator
43 implements ODEStateInterpolator {
44
45 /** Serializable UID. */
46 private static final long serialVersionUID = 20160328L;
47
48 /** Global previous state. */
49 private final ODEStateAndDerivative globalPreviousState;
50
51 /** Global current state. */
52 private final ODEStateAndDerivative globalCurrentState;
53
54 /** Soft previous state. */
55 private final ODEStateAndDerivative softPreviousState;
56
57 /** Soft current state. */
58 private final ODEStateAndDerivative softCurrentState;
59
60 /** integration direction. */
61 private final boolean forward;
62
63 /** Mapper for ODE equations primary and secondary components. */
64 private EquationsMapper mapper;
65
66 /** Simple constructor.
67 * @param isForward integration direction indicator
68 * @param globalPreviousState start of the global step
69 * @param globalCurrentState end of the global step
70 * @param softPreviousState start of the restricted step
71 * @param softCurrentState end of the restricted step
72 * @param equationsMapper mapper for ODE equations primary and secondary components
73 */
74 protected AbstractODEStateInterpolator(final boolean isForward,
75 final ODEStateAndDerivative globalPreviousState,
76 final ODEStateAndDerivative globalCurrentState,
77 final ODEStateAndDerivative softPreviousState,
78 final ODEStateAndDerivative softCurrentState,
79 final EquationsMapper equationsMapper) {
80 this.forward = isForward;
81 this.globalPreviousState = globalPreviousState;
82 this.globalCurrentState = globalCurrentState;
83 this.softPreviousState = softPreviousState;
84 this.softCurrentState = softCurrentState;
85 this.mapper = equationsMapper;
86 }
87
88 /** Create a new restricted version of the instance.
89 * <p>
90 * The instance is not changed at all.
91 * </p>
92 * @param previousState start of the restricted step
93 * @param currentState end of the restricted step
94 * @return restricted version of the instance
95 * @see #getPreviousState()
96 * @see #getCurrentState()
97 */
98 public AbstractODEStateInterpolator restrictStep(final ODEStateAndDerivative previousState,
99 final ODEStateAndDerivative currentState) {
100 return create(forward, globalPreviousState, globalCurrentState, previousState, currentState, mapper);
101 }
102
103 /** Create a new instance.
104 * @param newForward integration direction indicator
105 * @param newGlobalPreviousState start of the global step
106 * @param newGlobalCurrentState end of the global step
107 * @param newSoftPreviousState start of the restricted step
108 * @param newSoftCurrentState end of the restricted step
109 * @param newMapper equations mapper for the all equations
110 * @return a new instance
111 */
112 protected abstract AbstractODEStateInterpolator create(boolean newForward,
113 ODEStateAndDerivative newGlobalPreviousState,
114 ODEStateAndDerivative newGlobalCurrentState,
115 ODEStateAndDerivative newSoftPreviousState,
116 ODEStateAndDerivative newSoftCurrentState,
117 EquationsMapper newMapper);
118
119 /**
120 * Get the previous global grid point state.
121 * @return previous global grid point state
122 */
123 public ODEStateAndDerivative getGlobalPreviousState() {
124 return globalPreviousState;
125 }
126
127 /**
128 * Get the current global grid point state.
129 * @return current global grid point state
130 */
131 public ODEStateAndDerivative getGlobalCurrentState() {
132 return globalCurrentState;
133 }
134
135 /** {@inheritDoc} */
136 @Override
137 public ODEStateAndDerivative getPreviousState() {
138 return softPreviousState;
139 }
140
141 /** {@inheritDoc} */
142 @Override
143 public boolean isPreviousStateInterpolated() {
144 return softPreviousState != globalPreviousState;
145 }
146
147 /** {@inheritDoc} */
148 @Override
149 public ODEStateAndDerivative getCurrentState() {
150 return softCurrentState;
151 }
152
153 /** {@inheritDoc} */
154 @Override
155 public boolean isCurrentStateInterpolated() {
156 return softCurrentState != globalCurrentState;
157 }
158
159 /** {@inheritDoc} */
160 @Override
161 public ODEStateAndDerivative getInterpolatedState(final double time) {
162 if (FastMath.abs(globalCurrentState.getTime() - globalPreviousState.getTime()) <=
163 FastMath.ulp(globalCurrentState.getTime())) {
164 return globalCurrentState;
165 }
166 final double thetaH = time - globalPreviousState.getTime();
167 final double oneMinusThetaH = globalCurrentState.getTime() - time;
168 final double theta = thetaH / (globalCurrentState.getTime() - globalPreviousState.getTime());
169 return computeInterpolatedStateAndDerivatives(mapper, time, theta, thetaH, oneMinusThetaH);
170 }
171
172 /** {@inheritDoc} */
173 @Override
174 public boolean isForward() {
175 return forward;
176 }
177
178 /** Get the mapper for ODE equations primary and secondary components.
179 * @return mapper for ODE equations primary and secondary components
180 */
181 protected EquationsMapper getMapper() {
182 return mapper;
183 }
184
185 /** Compute the state and derivatives at the interpolated time.
186 * This is the main processing method that should be implemented by
187 * the derived classes to perform the interpolation.
188 * @param equationsMapper mapper for ODE equations primary and secondary components
189 * @param time interpolation time
190 * @param theta normalized interpolation abscissa within the step
191 * (theta is zero at the previous time step and one at the current time step)
192 * @param thetaH time gap between the previous time and the interpolated time
193 * @param oneMinusThetaH time gap between the interpolated time and
194 * the current time
195 * @return interpolated state and derivatives
196 * @exception MathIllegalStateException if the number of functions evaluations is exceeded
197 */
198 protected abstract ODEStateAndDerivative computeInterpolatedStateAndDerivatives(EquationsMapper equationsMapper,
199 double time, double theta,
200 double thetaH, double oneMinusThetaH)
201 throws MathIllegalStateException;
202
203 }