BooleanDetector.java

  1. /* Contributed in the public domain.
  2.  * Licensed to CS Systèmes d'Information (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.  */
  17. package org.orekit.propagation.events;


  20. import java.util.ArrayList;
  21. import java.util.Arrays;
  22. import java.util.Collection;
  23. import java.util.List;
  24. import java.util.NoSuchElementException;

  26. import org.hipparchus.util.FastMath;
  27. import org.orekit.propagation.SpacecraftState;
  28. import org.orekit.propagation.events.handlers.ContinueOnEvent;
  29. import org.orekit.propagation.events.handlers.EventHandler;
  30. import org.orekit.time.AbsoluteDate;

  32. /**
  33.  * This class provides AND and OR operations for event detectors. This class treats
  34.  * positive values of the g function as true and negative values as false.
  35.  *
  36.  * <p> One example for an imaging satellite might be to only detect events when a
  37.  * satellite is overhead (elevation &gt; 0) AND when the ground point is sunlit (Sun
  38.  * elevation &gt; 0). Another slightly contrived example using the OR operator would be to
  39.  * detect access to a set of ground stations and only report events when the satellite
  40.  * enters or leaves the field of view of the set, but not hand-offs between the ground
  41.  * stations.
  42.  *
  43.  * <p> For the BooleanDetector is important that the sign of the g function of the
  44.  * underlying event detector is not arbitrary, but has a semantic meaning, e.g. in or out,
  45.  * true or false. This class works well with event detectors that detect entry to or exit
  46.  * from a region, e.g. {@link EclipseDetector}, {@link ElevationDetector}, {@link
  47.  * LatitudeCrossingDetector}. Using this detector with detectors that are not based on
  48.  * entry to or exit from a region, e.g. {@link DateDetector}, {@link
  49.  * LongitudeCrossingDetector}, will likely lead to unexpected results. To apply conditions
  50.  * to this latter type of event detectors a {@link EventEnablingPredicateFilter} is
  51.  * usually more appropriate.
  52.  *
  53.  * @author Evan Ward
  54.  * @see #andCombine(Collection)
  55.  * @see #orCombine(Collection)
  56.  * @see #notCombine(EventDetector)
  57.  * @see EventEnablingPredicateFilter
  58.  * @see EventSlopeFilter
  59.  */
  60. public class BooleanDetector extends AbstractDetector<BooleanDetector> {

  62.     /** Serializable UID. */
  63.     private static final long serialVersionUID = 20170410L;

  65.     /** Original detectors: the operands. */
  66.     private final List<EventDetector> detectors;

  68.     /** The composition function. Should be associative for predictable behavior. */
  69.     private final Operator operator;

  71.     /**
  72.      * Private constructor with all the parameters.
  73.      *
  74.      * @param detectors    the operands.
  75.      * @param operator     reduction operator to apply to value of the g function of the
  76.      *                     operands.
  77.      * @param newMaxCheck  max check interval in seconds.
  78.      * @param newThreshold convergence threshold in seconds.
  79.      * @param newMaxIter   max iterations.
  80.      * @param newHandler   event handler.
  81.      */
  82.     private BooleanDetector(final List<EventDetector> detectors,
  83.                             final Operator operator,
  84.                             final double newMaxCheck,
  85.                             final double newThreshold,
  86.                             final int newMaxIter,
  87.                             final EventHandler<? super BooleanDetector> newHandler) {
  88.         super(newMaxCheck, newThreshold, newMaxIter, newHandler);
  89.         this.detectors = detectors;
  90.         this.operator = operator;
  91.     }

  93.     /**
  94.      * Create a new event detector that is the logical AND of the given event detectors.
  95.      *
  96.      * <p> The created event detector's g function is positive if and only if the g
  97.      * functions of all detectors in {@code detectors} are positive.
  98.      *
  99.      * <p> The starting interval, threshold, and iteration count are set to the most
  100.      * stringent (minimum) of all the {@code detectors}. The event handlers of the
  101.      * underlying {@code detectors} are not used, instead the default handler is {@link
  102.      * ContinueOnEvent}.
  103.      *
  104.      * @param detectors the operands. Must contain at least one detector.
  105.      * @return a new event detector that is the logical AND of the operands.
  106.      * @throws NoSuchElementException if {@code detectors} is empty.
  107.      * @see BooleanDetector
  108.      * @see #andCombine(Collection)
  109.      * @see #orCombine(EventDetector...)
  110.      * @see #notCombine(EventDetector)
  111.      */
  112.     public static BooleanDetector andCombine(final EventDetector... detectors) {
  113.         return andCombine(Arrays.asList(detectors));
  114.     }

  116.     /**
  117.      * Create a new event detector that is the logical AND of the given event detectors.
  118.      *
  119.      * <p> The created event detector's g function is positive if and only if the g
  120.      * functions of all detectors in {@code detectors} are positive.
  121.      *
  122.      * <p> The starting interval, threshold, and iteration count are set to the most
  123.      * stringent (minimum) of the {@code detectors}. The event handlers of the
  124.      * underlying {@code detectors} are not used, instead the default handler is {@link
  125.      * ContinueOnEvent}.
  126.      *
  127.      * @param detectors the operands. Must contain at least one detector.
  128.      * @return a new event detector that is the logical AND of the operands.
  129.      * @throws NoSuchElementException if {@code detectors} is empty.
  130.      * @see BooleanDetector
  131.      * @see #andCombine(EventDetector...)
  132.      * @see #orCombine(Collection)
  133.      * @see #notCombine(EventDetector)
  134.      */
  135.     public static BooleanDetector andCombine(final Collection<? extends EventDetector> detectors) {

  137.         return new BooleanDetector(new ArrayList<>(detectors), // copy for immutability
  138.                 Operator.AND,
  139.                 detectors.stream().map(EventDetector::getMaxCheckInterval).min(Double::compareTo).get(),
  140.                 detectors.stream().map(EventDetector::getThreshold).min(Double::compareTo).get(),
  141.                 detectors.stream().map(EventDetector::getMaxIterationCount).min(Integer::compareTo).get(),
  142.                 new ContinueOnEvent<>());
  143.     }

  145.     /**
  146.      * Create a new event detector that is the logical OR or the given event detectors.
  147.      *
  148.      * <p> The created event detector's g function is positive if and only if at least
  149.      * one of g functions of the event detectors in {@code detectors} is positive.
  150.      *
  151.      * <p> The starting interval, threshold, and iteration count are set to the most
  152.      * stringent (minimum) of the {@code detectors}. The event handlers of the
  153.      * underlying EventDetectors are not used, instead the default handler is {@link
  154.      * ContinueOnEvent}.
  155.      *
  156.      * @param detectors the operands. Must contain at least one detector.
  157.      * @return a new event detector that is the logical OR of the operands.
  158.      * @throws NoSuchElementException if {@code detectors} is empty.
  159.      * @see BooleanDetector
  160.      * @see #orCombine(Collection)
  161.      * @see #andCombine(EventDetector...)
  162.      * @see #notCombine(EventDetector)
  163.      */
  164.     public static BooleanDetector orCombine(final EventDetector... detectors) {
  165.         return orCombine(Arrays.asList(detectors));
  166.     }

  168.     /**
  169.      * Create a new event detector that is the logical OR or the given event detectors.
  170.      *
  171.      * <p> The created event detector's g function is positive if and only if at least
  172.      * one of g functions of the event detectors in {@code detectors} is positive.
  173.      *
  174.      * <p> The starting interval, threshold, and iteration count are set to the most
  175.      * stringent (minimum) of the {@code detectors}. The event handlers of the
  176.      * underlying EventDetectors are not used, instead the default handler is {@link
  177.      * ContinueOnEvent}.
  178.      *
  179.      * @param detectors the operands. Must contain at least one detector.
  180.      * @return a new event detector that is the logical OR of the operands.
  181.      * @throws NoSuchElementException if {@code detectors} is empty.
  182.      * @see BooleanDetector
  183.      * @see #orCombine(EventDetector...)
  184.      * @see #andCombine(Collection)
  185.      * @see #notCombine(EventDetector)
  186.      */
  187.     public static BooleanDetector orCombine(final Collection<? extends EventDetector> detectors) {

  189.         return new BooleanDetector(new ArrayList<>(detectors), // copy for immutability
  190.                 Operator.OR,
  191.                 detectors.stream().map(EventDetector::getMaxCheckInterval).min(Double::compareTo).get(),
  192.                 detectors.stream().map(EventDetector::getThreshold).min(Double::compareTo).get(),
  193.                 detectors.stream().map(EventDetector::getMaxIterationCount).min(Integer::compareTo).get(),
  194.                 new ContinueOnEvent<>());
  195.     }

  197.     /**
  198.      * Create a new event detector that negates the g function of another detector.
  199.      *
  200.      * <p> This detector will be initialized with the same {@link
  201.      * EventDetector#getMaxCheckInterval()}, {@link EventDetector#getThreshold()}, and
  202.      * {@link EventDetector#getMaxIterationCount()} as {@code detector}. The event handler
  203.      * of the underlying detector is not used, instead the default handler is {@link
  204.      * ContinueOnEvent}.
  205.      *
  206.      * @param detector to negate.
  207.      * @return an new event detector whose g function is the same magnitude but opposite
  208.      * sign of {@code detector}.
  209.      * @see #andCombine(Collection)
  210.      * @see #orCombine(Collection)
  211.      * @see BooleanDetector
  212.      */
  213.     public static NegateDetector notCombine(final EventDetector detector) {
  214.         return new NegateDetector(detector);
  215.     }

  217.     @Override
  218.     public double g(final SpacecraftState s) {
  219.         // can't use stream/lambda here because g(s) throws a checked exception
  220.         // so write out and combine the map and reduce loops
  221.         double ret = Double.NaN; // return value
  222.         boolean first = true;
  223.         for (final EventDetector detector : detectors) {
  224.             if (first) {
  225.                 ret = detector.g(s);
  226.                 first = false;
  227.             } else {
  228.                 ret = operator.combine(ret, detector.g(s));
  229.             }
  230.         }
  231.         // return the result of applying the operator to all operands
  232.         return ret;
  233.     }

  235.     @Override
  236.     protected BooleanDetector create(final double newMaxCheck,
  237.                                      final double newThreshold,
  238.                                      final int newMaxIter,
  239.                                      final EventHandler<? super BooleanDetector> newHandler) {
  240.         return new BooleanDetector(detectors, operator, newMaxCheck, newThreshold,
  241.                 newMaxIter, newHandler);
  242.     }

  244.     @Override
  245.     public void init(final SpacecraftState s0,
  246.                      final AbsoluteDate t) {
  247.         super.init(s0, t);
  248.         for (final EventDetector detector : detectors) {
  249.             detector.init(s0, t);
  250.         }
  251.     }

  253.     /** Local, serializable class for operator. */
  254.     private enum Operator {

  256.         /** And operator. */
  257.         AND() {

  259.             @Override
  260.             /** {@inheritDoc} */
  261.             public double combine(final double g1, final double g2) {
  262.                 return FastMath.min(g1, g2);
  263.             }

  265.         },

  267.         /** Or operator. */
  268.         OR() {

  270.             @Override
  271.             /** {@inheritDoc} */
  272.             public double combine(final double g1, final double g2) {
  273.                 return FastMath.max(g1, g2);
  274.             }

  276.         };

  278.         /** Combine two g functions evaluations.
  279.          * @param g1 first evaluation
  280.          * @param g2 second evaluation
  281.          * @return combined evaluation
  282.          */
  283.         public abstract double combine(double g1, double g2);

  285.     };

  287. }
Created with JaCoCo 0.8.2.201808211720