InterpolatingTransformProvider.java
/* Copyright 2002-2023 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.frames;
import java.io.Serializable;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.hipparchus.Field;
import org.hipparchus.CalculusFieldElement;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.AngularDerivativesFilter;
import org.orekit.utils.CartesianDerivativesFilter;
import org.orekit.utils.GenericTimeStampedCache;
/** Transform provider using thread-safe interpolation on transforms sample.
* <p>
* The interpolation is a polynomial Hermite interpolation, which
* can either use or ignore the derivatives provided by the raw
* provider. This means that simple raw providers that do not compute
* derivatives can be used, the derivatives will be added appropriately
* by the interpolation process.
* </p>
* @see GenericTimeStampedCache
* @see ShiftingTransformProvider
* @author Luc Maisonobe
*/
public class InterpolatingTransformProvider implements TransformProvider {
/** Serializable UID. */
private static final long serialVersionUID = 20140723L;
/** Provider for raw (non-interpolated) transforms. */
private final TransformProvider rawProvider;
/** Filter for Cartesian derivatives to use in interpolation. */
private final CartesianDerivativesFilter cFilter;
/** Filter for angular derivatives to use in interpolation. */
private final AngularDerivativesFilter aFilter;
/** Grid points time step. */
private final double step;
/** Cache for sample points. */
private final transient GenericTimeStampedCache<Transform> cache;
/** Field caches for sample points. */
// we use Object as the value of fieldCaches because despite numerous attempts,
// we could not find a way to use GenericTimeStampedCache<FieldTransform<? extends CalculusFieldElement<?>>
// without the compiler complaining
private final transient Map<Field<? extends CalculusFieldElement<?>>, Object> fieldCaches;
/** Simple constructor.
* @param rawProvider provider for raw (non-interpolated) transforms
* @param cFilter filter for derivatives from the sample to use in interpolation
* @param aFilter filter for derivatives from the sample to use in interpolation
* @param gridPoints number of interpolation grid points
* @param step grid points time step
* @param maxSlots maximum number of independent cached time slots
* in the {@link GenericTimeStampedCache time-stamped cache}
* @param maxSpan maximum duration span in seconds of one slot
* in the {@link GenericTimeStampedCache time-stamped cache}
* @param newSlotInterval time interval above which a new slot is created
* in the {@link GenericTimeStampedCache time-stamped cache}
* @since 9.1
*/
public InterpolatingTransformProvider(final TransformProvider rawProvider,
final CartesianDerivativesFilter cFilter,
final AngularDerivativesFilter aFilter,
final int gridPoints, final double step,
final int maxSlots, final double maxSpan, final double newSlotInterval) {
this.rawProvider = rawProvider;
this.cFilter = cFilter;
this.aFilter = aFilter;
this.step = step;
this.cache = new GenericTimeStampedCache<Transform>(gridPoints, maxSlots, maxSpan, newSlotInterval,
new TransformGenerator(gridPoints,
rawProvider,
step));
this.fieldCaches = new HashMap<>();
}
/** Get the underlying provider for raw (non-interpolated) transforms.
* @return provider for raw (non-interpolated) transforms
*/
public TransformProvider getRawProvider() {
return rawProvider;
}
/** Get the number of interpolation grid points.
* @return number of interpolation grid points
*/
public int getGridPoints() {
return cache.getMaxNeighborsSize();
}
/** Get the grid points time step.
* @return grid points time step
*/
public double getStep() {
return step;
}
/** {@inheritDoc} */
@Override
public Transform getTransform(final AbsoluteDate date) {
// retrieve a sample from the thread-safe cache
final List<Transform> sample = cache.getNeighbors(date).collect(Collectors.toList());
// interpolate to specified date
return Transform.interpolate(date, cFilter, aFilter, sample);
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
@SuppressWarnings("unchecked")
GenericTimeStampedCache<FieldTransform<T>> fieldCache =
(GenericTimeStampedCache<FieldTransform<T>>) fieldCaches.get(date.getField());
if (fieldCache == null) {
fieldCache =
new GenericTimeStampedCache<FieldTransform<T>>(cache.getMaxNeighborsSize(),
cache.getMaxSlots(),
cache.getMaxSpan(),
cache.getNewSlotQuantumGap(),
new FieldTransformGenerator<>(date.getField(),
cache.getMaxNeighborsSize(),
rawProvider,
step));
fieldCaches.put(date.getField(), fieldCache);
}
// retrieve a sample from the thread-safe cache
final Stream<FieldTransform<T>> sample = fieldCache.getNeighbors(date.toAbsoluteDate());
// interpolate to specified date
return FieldTransform.interpolate(date, cFilter, aFilter, sample);
}
/** Replace the instance with a data transfer object for serialization.
* <p>
* This intermediate class serializes only the data needed for generation,
* but does <em>not</em> serializes the cache itself (in fact the cache is
* not serializable).
* </p>
* @return data transfer object that will be serialized
*/
private Object writeReplace() {
return new DTO(rawProvider, cFilter.getMaxOrder(), aFilter.getMaxOrder(),
cache.getMaxNeighborsSize(), step,
cache.getMaxSlots(), cache.getMaxSpan(), cache.getNewSlotQuantumGap());
}
/** Internal class used only for serialization. */
private static class DTO implements Serializable {
/** Serializable UID. */
private static final long serialVersionUID = 20170823L;
/** Provider for raw (non-interpolated) transforms. */
private final TransformProvider rawProvider;
/** Cartesian derivatives to use in interpolation. */
private final int cDerivatives;
/** Angular derivatives to use in interpolation. */
private final int aDerivatives;
/** Number of grid points. */
private final int gridPoints;
/** Grid points time step. */
private final double step;
/** Maximum number of independent cached time slots. */
private final int maxSlots;
/** Maximum duration span in seconds of one slot. */
private final double maxSpan;
/** Time interval above which a new slot is created. */
private final double newSlotInterval;
/** Simple constructor.
* @param rawProvider provider for raw (non-interpolated) transforms
* @param cDerivatives derivation order for Cartesian coordinates
* @param aDerivatives derivation order for angular coordinates
* @param gridPoints number of interpolation grid points
* @param step grid points time step
* @param maxSlots maximum number of independent cached time slots
* in the {@link GenericTimeStampedCache time-stamped cache}
* @param maxSpan maximum duration span in seconds of one slot
* in the {@link GenericTimeStampedCache time-stamped cache}
* @param newSlotInterval time interval above which a new slot is created
* in the {@link GenericTimeStampedCache time-stamped cache}
*/
private DTO(final TransformProvider rawProvider, final int cDerivatives, final int aDerivatives,
final int gridPoints, final double step,
final int maxSlots, final double maxSpan, final double newSlotInterval) {
this.rawProvider = rawProvider;
this.cDerivatives = cDerivatives;
this.aDerivatives = aDerivatives;
this.gridPoints = gridPoints;
this.step = step;
this.maxSlots = maxSlots;
this.maxSpan = maxSpan;
this.newSlotInterval = newSlotInterval;
}
/** Replace the deserialized data transfer object with a {@link InterpolatingTransformProvider}.
* @return replacement {@link InterpolatingTransformProvider}
*/
private Object readResolve() {
// build a new provider, with an empty cache
return new InterpolatingTransformProvider(rawProvider,
CartesianDerivativesFilter.getFilter(cDerivatives),
AngularDerivativesFilter.getFilter(aDerivatives),
gridPoints, step,
maxSlots, maxSpan, newSlotInterval);
}
}
}