AbstractFieldTimeInterpolator.java
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* 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
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*
* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.time;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.Field;
import org.hipparchus.util.FastMath;
import org.orekit.errors.OrekitIllegalArgumentException;
import org.orekit.errors.OrekitInternalError;
import org.orekit.errors.OrekitMessages;
import org.orekit.utils.ImmutableFieldTimeStampedCache;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;
import java.util.stream.Stream;
/**
* Abstract class for time interpolator.
*
* @param <T> interpolated time stamped type
* @param <KK> type of the field element
*
* @author Vincent Cucchietti
*/
public abstract class AbstractFieldTimeInterpolator<T extends FieldTimeStamped<KK>, KK extends CalculusFieldElement<KK>>
implements FieldTimeInterpolator<T, KK> {
/** Default extrapolation time threshold: 1ms. */
public static final double DEFAULT_EXTRAPOLATION_THRESHOLD_SEC = 1e-3;
/** Default number of interpolation points. */
public static final int DEFAULT_INTERPOLATION_POINTS = 2;
/** The extrapolation threshold beyond which the propagation will fail. */
private final double extrapolationThreshold;
/** Neighbor size. */
private final int interpolationPoints;
/**
* Constructor.
*
* @param interpolationPoints number of interpolation points
* @param extrapolationThreshold extrapolation threshold beyond which the propagation will fail
*/
public AbstractFieldTimeInterpolator(final int interpolationPoints, final double extrapolationThreshold) {
this.interpolationPoints = interpolationPoints;
this.extrapolationThreshold = extrapolationThreshold;
}
/**
* Method checking if given interpolator is compatible with given sample size.
*
* @param interpolator interpolator
* @param sampleSize sample size
* @param <T> type of the field elements
*/
public static <T extends CalculusFieldElement<T>> void checkInterpolatorCompatibilityWithSampleSize(
final FieldTimeInterpolator<? extends FieldTimeStamped<T>, T> interpolator,
final int sampleSize) {
// Retrieve all sub-interpolators (or a singleton list with given interpolator if there are no sub-interpolators)
final List<FieldTimeInterpolator<? extends FieldTimeStamped<T>, T>> subInterpolators =
interpolator.getSubInterpolators();
for (final FieldTimeInterpolator<? extends FieldTimeStamped<T>, T> subInterpolator : subInterpolators) {
if (sampleSize < subInterpolator.getNbInterpolationPoints()) {
throw new OrekitIllegalArgumentException(OrekitMessages.NOT_ENOUGH_DATA, sampleSize);
}
}
}
/** {@inheritDoc} */
@Override
public T interpolate(final FieldAbsoluteDate<KK> interpolationDate, final Stream<T> sample) {
return interpolate(interpolationDate, sample.collect(Collectors.toList()));
}
/** {@inheritDoc}. */
@Override
public T interpolate(final FieldAbsoluteDate<KK> interpolationDate, final Collection<T> sample) {
final InterpolationData interpolationData = new InterpolationData(interpolationDate, sample);
return interpolate(interpolationData);
}
/**
* Get the central date to use to find neighbors while taking into account extrapolation threshold.
*
* @param date interpolation date
* @param cachedSamples cached samples
* @param threshold extrapolation threshold
* @param <T> type of time stamped element
* @param <KK> type of calculus field element
*
* @return central date to use to find neighbors
* @since 12.0.1
*/
public static <T extends FieldTimeStamped<KK>, KK extends CalculusFieldElement<KK>> FieldAbsoluteDate<KK> getCentralDate(
final FieldAbsoluteDate<KK> date,
final ImmutableFieldTimeStampedCache<T, KK> cachedSamples,
final double threshold) {
return getCentralDate(
date,
cachedSamples.getEarliest().getDate(),
cachedSamples.getLatest().getDate(),
threshold);
}
/**
* Get the central date to use to find neighbors while taking into account extrapolation threshold.
*
* @param date interpolation date
* @param minDate earliest date in the sample.
* @param maxDate latest date in the sample.
* @param threshold extrapolation threshold
* @param <KK> type of calculus field element
*
* @return central date to use to find neighbors
* @since 12.0.1
*/
public static <KK extends CalculusFieldElement<KK>> FieldAbsoluteDate<KK> getCentralDate(
final FieldAbsoluteDate<KK> date,
final FieldAbsoluteDate<KK> minDate,
final FieldAbsoluteDate<KK> maxDate,
final double threshold) {
final FieldAbsoluteDate<KK> central;
if (date.compareTo(minDate) < 0 && FastMath.abs(date.durationFrom(minDate)).getReal() <= threshold) {
// avoid TimeStampedCacheException as we are still within the tolerance before minDate
central = minDate;
} else if (date.compareTo(maxDate) > 0 && FastMath.abs(date.durationFrom(maxDate)).getReal() <= threshold) {
// avoid TimeStampedCacheException as we are still within the tolerance after maxDate
central = maxDate;
} else {
central = date;
}
return central;
}
/** {@inheritDoc} */
public List<FieldTimeInterpolator<? extends FieldTimeStamped<KK>, KK>> getSubInterpolators() {
return Collections.singletonList(this);
}
/** {@inheritDoc} */
public int getNbInterpolationPoints() {
final List<FieldTimeInterpolator<? extends FieldTimeStamped<KK>, KK>> subInterpolators = getSubInterpolators();
// In case the interpolator does not have sub interpolators
if (subInterpolators.size() == 1) {
return interpolationPoints;
}
// Otherwise find maximum number of interpolation points among sub interpolators
else {
final Optional<Integer> optionalMaxNbInterpolationPoints =
subInterpolators.stream().map(FieldTimeInterpolator::getNbInterpolationPoints).max(Integer::compareTo);
if (optionalMaxNbInterpolationPoints.isPresent()) {
return optionalMaxNbInterpolationPoints.get();
} else {
// This should never happen
throw new OrekitInternalError(null);
}
}
}
/** {@inheritDoc} */
public double getExtrapolationThreshold() {
return extrapolationThreshold;
}
/**
* Add all lowest level sub interpolators to the sub interpolator list.
*
* @param subInterpolator optional sub interpolator to add
* @param subInterpolators list of sub interpolators
* @param <S> type of the field element
*/
protected <S extends CalculusFieldElement<S>> void addOptionalSubInterpolatorIfDefined(
final FieldTimeInterpolator<? extends FieldTimeStamped<S>, S> subInterpolator,
final List<FieldTimeInterpolator<? extends FieldTimeStamped<S>, S>> subInterpolators) {
// Add all lowest level sub interpolators
if (subInterpolator != null) {
subInterpolators.addAll(subInterpolator.getSubInterpolators());
}
}
/**
* Interpolate instance from given interpolation data.
*
* @param interpolationData interpolation data
*
* @return interpolated instance from given interpolation data.
*/
protected abstract T interpolate(InterpolationData interpolationData);
/**
* Get the time parameter which lies between [0:1] by normalizing the difference between interpolating time and previous
* date by the Δt between tabulated values.
*
* @param interpolatingTime time at which we want to interpolate a value (between previous and next tabulated dates)
* @param previousDate previous tabulated value date
* @param nextDate next tabulated value date
*
* @return time parameter which lies between [0:1]
*/
protected KK getTimeParameter(final FieldAbsoluteDate<KK> interpolatingTime,
final FieldAbsoluteDate<KK> previousDate,
final FieldAbsoluteDate<KK> nextDate) {
return interpolatingTime.durationFrom(previousDate).divide(nextDate.getDate().durationFrom(previousDate));
}
/**
* Nested class used to store interpolation data.
* <p>
* It makes the interpolator thread safe.
*/
public class InterpolationData {
/** Interpolation date. */
private final FieldAbsoluteDate<KK> interpolationDate;
/** Unmodifiable list of neighbors. */
private final List<T> neighborList;
/** Field of the element. */
private final Field<KK> field;
/** Fielded zero. */
private final KK zero;
/** Fielded one. */
private final KK one;
/**
* Constructor.
*
* @param interpolationDate interpolation date
* @param sample time stamped sample
*/
protected InterpolationData(final FieldAbsoluteDate<KK> interpolationDate, final Collection<T> sample) {
// Handle specific case that is not handled by the immutable time stamped cache constructor
if (sample.isEmpty()) {
throw new OrekitIllegalArgumentException(OrekitMessages.NOT_ENOUGH_DATA, 0);
}
// TODO performance: create neighborsList without copying sample.
if (sample.size() == interpolationPoints) {
// shortcut for simple case
// copy list to make neighborList immutable
this.neighborList = Collections.unmodifiableList(new ArrayList<>(sample));
} else {
// else, select sample.
// Create immutable time stamped cache
final ImmutableFieldTimeStampedCache<T, KK> cachedSamples =
new ImmutableFieldTimeStampedCache<>(interpolationPoints, sample);
// Find neighbors
final FieldAbsoluteDate<KK> central =
AbstractFieldTimeInterpolator.getCentralDate(
interpolationDate,
cachedSamples,
extrapolationThreshold);
final Stream<T> neighborsStream = cachedSamples.getNeighbors(central);
// Convert to unmodifiable list
neighborList = Collections.unmodifiableList(neighborsStream.collect(Collectors.toList()));
}
// Extract field and useful terms
this.field = interpolationDate.getField();
this.zero = field.getZero();
this.one = field.getOne();
// Store interpolation date
this.interpolationDate = interpolationDate;
}
/** Get interpolation date.
* @return interpolation date
*/
public FieldAbsoluteDate<KK> getInterpolationDate() {
return interpolationDate;
}
/** Get neighbor list.
* @return neighbor list
*/
public List<T> getNeighborList() {
return neighborList;
}
/** Get field.
* @return field
*/
public Field<KK> getField() {
return field;
}
/** Get zero.
* @return zero
*/
public KK getZero() {
return zero;
}
/** Get one.
* @return one
*/
public KK getOne() {
return one;
}
}
}