Generator.java
/* Copyright 2002-2024 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
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*/
package org.orekit.estimation.measurements.generation;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.SortedSet;
import java.util.TreeSet;
import org.orekit.estimation.measurements.EstimatedMeasurementBase;
import org.orekit.estimation.measurements.ObservableSatellite;
import org.orekit.estimation.measurements.ObservedMeasurement;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.PropagatorsParallelizer;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.sampling.MultiSatStepHandler;
import org.orekit.propagation.sampling.OrekitStepHandler;
import org.orekit.propagation.sampling.OrekitStepInterpolator;
import org.orekit.propagation.sampling.StepHandlerMultiplexer;
import org.orekit.time.AbsoluteDate;
/** Main generator for {@link ObservedMeasurement observed measurements}.
* @author Luc Maisonobe
* @since 9.3
*/
public class Generator {
/** Observable satellites.
* @since 12.0
*/
private final List<ObservableSatellite> observableSatellites;
/** Propagators. */
private final List<Propagator> propagators;
/** Schedulers for multiple satellites measurements. */
private final List<Scheduler<? extends ObservedMeasurement<?>>> multiSatSchedulers;
/** Schedulers for single satellite measurements. */
private final Map<ObservableSatellite, List<Scheduler<? extends ObservedMeasurement<?>>>> singleSatSchedulers;
/** Subscribers for generated measurements events.
* @since 12.0
*/
private final List<GeneratedMeasurementSubscriber> subscribers;
/** Build a generator with no sequences generator.
*/
public Generator() {
this.observableSatellites = new ArrayList<>();
this.propagators = new ArrayList<>();
this.multiSatSchedulers = new ArrayList<>();
this.singleSatSchedulers = new HashMap<>();
this.subscribers = new ArrayList<>();
}
/** Add a propagator.
* @param propagator to add
* @return satellite satellite propagated by the propagator
*/
public ObservableSatellite addPropagator(final Propagator propagator) {
final ObservableSatellite os = new ObservableSatellite(propagators.size());
observableSatellites.add(os);
propagators.add(propagator);
return os;
}
/** Get a registered propagator.
* @param satellite satellite propagated by the propagator {@link #addPropagator(Propagator)}
* @return propagator corresponding to satellite
*/
public Propagator getPropagator(final ObservableSatellite satellite) {
return propagators.get(satellite.getPropagatorIndex());
}
/** Add a sequences generator for a specific measurement type.
* @param scheduler sequences generator to add
* @param <T> the type of the measurement
*/
public <T extends ObservedMeasurement<T>> void addScheduler(final Scheduler<T> scheduler) {
final ObservableSatellite[] satellites = scheduler.getBuilder().getSatellites();
if (satellites.length == 1) {
// this scheduler manages only one satellite
// we can let the individual propagator handle it
final List<Scheduler<? extends ObservedMeasurement<?>>> list =
singleSatSchedulers.computeIfAbsent(satellites[0], k -> new ArrayList<>());
list.add(scheduler);
} else {
// this scheduler manages several satellites at once
// we need to handle it at top level
multiSatSchedulers.add(scheduler);
}
}
/** Add a subscriber.
* @param subscriber to add
* @see GatheringSubscriber
* @since 12.0
*/
public void addSubscriber(final GeneratedMeasurementSubscriber subscriber) {
subscribers.add(subscriber);
}
/** Generate measurements.
* @param start start of the measurements time span
* @param end end of the measurements time span
*/
public void generate(final AbsoluteDate start, final AbsoluteDate end) {
// set up top level handler
final MultipleSatGeneratorHandler globalHandler =
new MultipleSatGeneratorHandler(multiSatSchedulers, subscribers,
observableSatellites, end.isAfterOrEqualTo(start));
// set up low level handlers
for (final Map.Entry<ObservableSatellite, List<Scheduler<? extends ObservedMeasurement<?>>>> entry : singleSatSchedulers.entrySet()) {
final StepHandlerMultiplexer multiplexer = propagators.get(entry.getKey().getPropagatorIndex()).getMultiplexer();
for (final Scheduler<?> scheduler : entry.getValue()) {
multiplexer.add(new SingleSatGeneratorHandler<>(scheduler, globalHandler));
}
}
// prepare parallelized generation
final PropagatorsParallelizer parallelizer = new PropagatorsParallelizer(propagators, globalHandler);
// generate the measurements
parallelizer.propagate(start, end);
// clean up low level handlers
for (final Map.Entry<ObservableSatellite, List<Scheduler<? extends ObservedMeasurement<?>>>> entry : singleSatSchedulers.entrySet()) {
// we need to clean up the step handlers in two loops to avoid concurrent modification exception
final StepHandlerMultiplexer multiplexer = propagators.get(entry.getKey().getPropagatorIndex()).getMultiplexer();
final List<OrekitStepHandler> toBeRemoved = new ArrayList<>();
for (final OrekitStepHandler handler : multiplexer.getHandlers()) {
if (handler instanceof SingleSatGeneratorHandler &&
((SingleSatGeneratorHandler<?>) handler).globalHandler == globalHandler) {
toBeRemoved.add(handler);
}
}
for (final OrekitStepHandler handler : toBeRemoved) {
multiplexer.remove(handler);
}
}
}
/** Handler for measurements generation steps, single satellite case.
* <p>
* These handlers are called from the individual propagators threads.
* This means they generate measurements in parallel.
* </p>
* @param <T> the type of the measurement
* @since 12.0
*/
private static class SingleSatGeneratorHandler<T extends ObservedMeasurement<T>> implements OrekitStepHandler {
/** Scheduler. */
private final Scheduler<T> scheduler;
/** Satellite related to this scheduler. */
private final ObservableSatellite satellite;
/** Global handler. */
private final MultipleSatGeneratorHandler globalHandler;
/** Simple constructor.
* @param scheduler scheduler
* @param globalHandler global handler
*/
SingleSatGeneratorHandler(final Scheduler<T> scheduler, final MultipleSatGeneratorHandler globalHandler) {
this.scheduler = scheduler;
this.satellite = scheduler.getBuilder().getSatellites()[0];
this.globalHandler = globalHandler;
}
/** {@inheritDoc} */
@Override
public void init(final SpacecraftState state0, final AbsoluteDate t) {
scheduler.init(state0.getDate(), t);
}
/** {@inheritDoc} */
@Override
public void handleStep(final OrekitStepInterpolator interpolator) {
globalHandler.addMeasurements(scheduler.generate(Collections.singletonMap(satellite, interpolator)));
}
}
/** Handler for measurements generation steps.
* <p>
* This handler is called from the propagator parallelizer thread.
* The parallelizer thread is called after the individual propagators thread,
* which may already have produced measurements ahead of time, so we must
* take care than within each step we handle only the measurements that belong
* to this step.
* </p>
*/
private static class MultipleSatGeneratorHandler implements MultiSatStepHandler {
/** Sequences generators. */
private final List<Scheduler<? extends ObservedMeasurement<?>>> schedulers;
/** Subscribers for generated measurements events.
* @since 12.0
*/
private final List<GeneratedMeasurementSubscriber> subscribers;
/** Observable satellites.
* @since 12.0
*/
private final List<ObservableSatellite> observableSatellites;
/** Storage for sorted measurements within one step.
* @since 12.0
*/
private final SortedSet<EstimatedMeasurementBase<?>> generated;
/** Forward generation indicator.
* @since 12.0
*/
private final boolean forward;
/** Simple constructor.
* @param schedulers sequences generators
* @param subscribers subscribers for generated measurements events
* @param observableSatellites observable satellites
* @param forward if true, generation is forward
* @since 12.0
*/
MultipleSatGeneratorHandler(final List<Scheduler<? extends ObservedMeasurement<?>>> schedulers,
final List<GeneratedMeasurementSubscriber> subscribers,
final List<ObservableSatellite> observableSatellites, final boolean forward) {
// measurements comparator, consistent with generation direction
final Comparator<EstimatedMeasurementBase<?>> comparator = forward ? Comparator.naturalOrder() : Comparator.reverseOrder();
this.schedulers = schedulers;
this.subscribers = subscribers;
this.observableSatellites = observableSatellites;
this.generated = new TreeSet<>(comparator);
this.forward = forward;
}
/** {@inheritDoc} */
@Override
public void init(final List<SpacecraftState> states0, final AbsoluteDate t) {
final AbsoluteDate start = states0.get(0).getDate();
// initialize schedulers
for (final Scheduler<?> scheduler : schedulers) {
scheduler.init(start, t);
}
// initialize subscribers
for (final GeneratedMeasurementSubscriber subscriber : subscribers) {
subscriber.init(start, t);
}
}
/** {@inheritDoc} */
@Override
public void handleStep(final List<OrekitStepInterpolator> interpolators) {
// prepare interpolators map
final Map<ObservableSatellite, OrekitStepInterpolator> interpolatorsMap =
new HashMap<>(interpolators.size());
for (int i = 0; i < interpolators.size(); ++i) {
interpolatorsMap.put(observableSatellites.get(i), interpolators.get(i));
}
final AbsoluteDate lastDate = interpolators.get(0).getCurrentState().getDate();
synchronized (generated) {
// generate measurements, looping over schedulers
for (final Scheduler<? extends ObservedMeasurement<?>> scheduler : schedulers) {
generated.addAll(scheduler.generate(interpolatorsMap));
}
// now that we have all measurements properly sorted, we can feed them to subscribers
for (final Iterator<EstimatedMeasurementBase<?>> iterator = generated.iterator(); iterator.hasNext();) {
final EstimatedMeasurementBase<?> measurement = iterator.next();
if (forward == lastDate.isAfterOrEqualTo(measurement)) {
// this measurement belongs to the current step
for (final GeneratedMeasurementSubscriber subscriber : subscribers) {
subscriber.handleGeneratedMeasurement(measurement);
}
iterator.remove();
} else {
// this measurement belongs to an upcoming step ; we don't handle it yet as more
// intermediate measurements may be produced by low level propagators threads
break;
}
}
}
}
/** {@inheritDoc} */
public void finish(final List<SpacecraftState> finalStates) {
synchronized (generated) {
for (final EstimatedMeasurementBase<?> measurement : generated) {
for (final GeneratedMeasurementSubscriber subscriber : subscribers) {
subscriber.handleGeneratedMeasurement(measurement);
}
}
generated.clear();
}
}
/** Add measurements performed by a low level handler.
* @param measurements measurements to add
* @since 12.0
*/
private void addMeasurements(final SortedSet<? extends EstimatedMeasurementBase<?>> measurements) {
synchronized (generated) {
generated.addAll(measurements);
}
}
}
}