ShiftingTransformProvider.java

  1. /* Copyright 2002-2025 CS GROUP
  2.  * Licensed to CS GROUP (CS) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * CS 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.  */

  18. package org.orekit.frames;

  20. import java.util.HashMap;
  21. import java.util.Map;

  23. import org.hipparchus.Field;
  24. import org.hipparchus.CalculusFieldElement;
  25. import org.hipparchus.util.FastMath;
  26. import org.orekit.time.AbsoluteDate;
  27. import org.orekit.time.FieldAbsoluteDate;
  28. import org.orekit.utils.AngularDerivativesFilter;
  29. import org.orekit.utils.CartesianDerivativesFilter;
  30. import org.orekit.utils.GenericTimeStampedCache;

  32. /** Transform provider using thread-safe shifts on transforms sample.
  33.  * <p>
  34.  * The shifts take derivatives into account, up to user specified order.
  35.  * </p>
  36.  * @see GenericTimeStampedCache
  37.  * @see InterpolatingTransformProvider
  38.  * @since 7.1
  39.  * @author Luc Maisonobe
  40.  */
  41. public class ShiftingTransformProvider implements TransformProvider {

  43.     /** First level cache. */
  44.     private final InterpolatingTransformProvider interpolatingProvider;

  46.     /** Cache for sample points. */
  47.     private final transient GenericTimeStampedCache<Transform> cache;

  49.     /** Field caches for sample points. */
  50.     // we use Object as the value of fieldCaches because despite numerous attempts,
  51.     // we could not find a way to use GenericTimeStampedCache<FieldTransform<? extends CalculusFieldElement<?>>
  52.     // without the compiler complaining
  53.     private final transient Map<Field<? extends CalculusFieldElement<?>>, Object> fieldCaches;

  55.     /** Simple constructor.
  56.      * @param rawProvider provider for raw (non-interpolated) transforms
  57.      * @param cFilter filter for derivatives from the sample to use in interpolation
  58.      * @param aFilter filter for derivatives from the sample to use in interpolation
  59.      * @param gridPoints number of interpolation grid points
  60.      * @param step grid points time step
  61.      * @param maxSlots maximum number of independent cached time slots
  62.      * in the {@link GenericTimeStampedCache time-stamped cache}
  63.      * @param maxSpan maximum duration span in seconds of one slot
  64.      * in the {@link GenericTimeStampedCache time-stamped cache}
  65.      * @param newSlotInterval time interval above which a new slot is created
  66.      * in the {@link GenericTimeStampedCache time-stamped cache}
  67.      * @since 9.1
  68.      */
  69.     public ShiftingTransformProvider(final TransformProvider rawProvider,
  70.                                      final CartesianDerivativesFilter cFilter,
  71.                                      final AngularDerivativesFilter aFilter,
  72.                                      final int gridPoints, final double step,
  73.                                      final int maxSlots, final double maxSpan, final double newSlotInterval) {
  74.         this(new InterpolatingTransformProvider(rawProvider, cFilter, aFilter,
  75.                                                 gridPoints, step, maxSlots, maxSpan, newSlotInterval),
  76.              maxSlots, maxSpan, newSlotInterval);
  77.     }

  79.     /** Simple constructor.
  80.      * @param interpolatingProvider first level cache provider
  81.      * @param maxSlots maximum number of independent cached time slots
  82.      * in the {@link GenericTimeStampedCache time-stamped cache}
  83.      * @param maxSpan maximum duration span in seconds of one slot
  84.      * in the {@link GenericTimeStampedCache time-stamped cache}
  85.      * @param newSlotInterval time interval above which a new slot is created
  86.      * in the {@link GenericTimeStampedCache time-stamped cache}
  87.      */
  88.     private ShiftingTransformProvider(final InterpolatingTransformProvider interpolatingProvider,
  89.                                      final int maxSlots, final double maxSpan, final double newSlotInterval) {
  90.         this.interpolatingProvider = interpolatingProvider;
  91.         this.cache = new GenericTimeStampedCache<>(2, maxSlots, maxSpan, newSlotInterval,
  92.                 new TransformGenerator(2,
  93.                         interpolatingProvider,
  94.                         interpolatingProvider.getStep()));
  95.         this.fieldCaches = new HashMap<>();
  96.     }

  98.     /** Get the underlying provider for raw (non-interpolated) transforms.
  99.      * @return provider for raw (non-interpolated) transforms
  100.      */
  101.     public TransformProvider getRawProvider() {
  102.         return interpolatingProvider.getRawProvider();
  103.     }

  105.     /** Get the number of interpolation grid points.
  106.      * @return number of interpolation grid points
  107.      */
  108.     public int getGridPoints() {
  109.         return interpolatingProvider.getGridPoints();
  110.     }

  112.     /** Get the grid points time step.
  113.      * @return grid points time step
  114.      */
  115.     public double getStep() {
  116.         return interpolatingProvider.getStep();
  117.     }

  119.     /** {@inheritDoc} */
  120.     public Transform getTransform(final AbsoluteDate date) {
  121.         // retrieve a sample from the thread-safe cache
  122.         final Transform closest = cache.getNeighbors(date).reduce((t0, t1) ->
  123.             FastMath.abs(date.durationFrom(t0.getDate())) < FastMath.abs(date.durationFrom(t1.getDate())) ? t0 : t1
  124.         ).get();
  125.         return closest.shiftedBy(date.durationFrom(closest.getDate()));
  126.     }

  128.     /** {@inheritDoc} */
  129.     @Override
  130.     public StaticTransform getStaticTransform(final AbsoluteDate date) {
  131.         // retrieve a sample from the thread-safe cache
  132.         final Transform closest = cache.getNeighbors(date).reduce((t0, t1) ->
  133.                 FastMath.abs(date.durationFrom(t0.getDate())) < FastMath.abs(date.durationFrom(t1.getDate())) ? t0 : t1
  134.         ).get();
  135.         return closest.staticShiftedBy(date.durationFrom(closest.getDate()));
  136.     }

  138.     /** {@inheritDoc} */
  139.     public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
  140.         @SuppressWarnings("unchecked")
  141.         GenericTimeStampedCache<FieldTransform<T>> fieldCache =
  142.             (GenericTimeStampedCache<FieldTransform<T>>) fieldCaches.get(date.getField());
  143.         if (fieldCache == null) {
  144.             fieldCache =
  145.                     new GenericTimeStampedCache<>(cache.getMaxNeighborsSize(),
  146.                             cache.getMaxSlots(),
  147.                             cache.getMaxSpan(),
  148.                             cache.getNewSlotQuantumGap(),
  149.                             new FieldTransformGenerator<>(date.getField(),
  150.                                     cache.getMaxNeighborsSize(),
  151.                                     interpolatingProvider,
  152.                                     interpolatingProvider.getStep()));
  153.             fieldCaches.put(date.getField(), fieldCache);
  154.         }

  156.         // retrieve a sample from the thread-safe cache
  157.         final FieldTransform<T> closest = fieldCache.getNeighbors(date.toAbsoluteDate()).reduce((t0, t1) ->
  158.             date.durationFrom(t0.getDate()).abs().getReal() < date.durationFrom(t1.getDate()).abs().getReal() ?
  159.             t0 : t1
  160.         ).get();
  161.         return closest.shiftedBy(date.durationFrom(closest.getDate()));
  162.     }

  164.     /** {@inheritDoc} */
  165.     @Override
  166.     public <T extends CalculusFieldElement<T>> FieldStaticTransform<T> getStaticTransform(final FieldAbsoluteDate<T> date) {
  167.         @SuppressWarnings("unchecked")
  168.         GenericTimeStampedCache<FieldTransform<T>> fieldCache =
  169.             (GenericTimeStampedCache<FieldTransform<T>>) fieldCaches.get(date.getField());
  170.         if (fieldCache == null) {
  171.             fieldCache =
  172.                     new GenericTimeStampedCache<>(cache.getMaxNeighborsSize(),
  173.                             cache.getMaxSlots(),
  174.                             cache.getMaxSpan(),
  175.                             cache.getNewSlotQuantumGap(),
  176.                             new FieldTransformGenerator<>(date.getField(),
  177.                                     cache.getMaxNeighborsSize(),
  178.                                     interpolatingProvider,
  179.                                     interpolatingProvider.getStep()));
  180.             fieldCaches.put(date.getField(), fieldCache);
  181.         }

  183.         // retrieve a sample from the thread-safe cache
  184.         final FieldTransform<T> closest = fieldCache.getNeighbors(date.toAbsoluteDate()).reduce((t0, t1) ->
  185.             date.durationFrom(t0.getDate()).abs().getReal() < date.durationFrom(t1.getDate()).abs().getReal() ?
  186.             t0 : t1
  187.         ).get();
  188.         return closest.staticShiftedBy(date.durationFrom(closest.getDate()));
  189.     }

  191. }
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