ParameterDriver.java
/* Copyright 2002-2026 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,
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package org.orekit.utils.drivers;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.hipparchus.analysis.differentiation.Gradient;
import org.hipparchus.exception.LocalizedCoreFormats;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.Precision;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.TimeInterval;
/** Class allowing to drive the value of a parameter.
* <p>
* This class is typically used as a bridge between an estimation algorithm
* (typically orbit determination or optimizer) and an internal parameter in
* a physical model that needs to be tuned. The physical model will expose to
* the algorithm a set of instances of this class so the algorithm can call the
* {@link #setValue(double)} method to update the parameter value.
* </p>
* <p>
* Any object can be notified when any of value, name, selection status… are changed.
* This is done by {@link #addObserver(ParameterObserver)} registering} a
* {@link ParameterObserver ParameterObserver} to the parameter driver.
* <p>
* This design has two major goals. First, it allows an external algorithm to drive
* internal parameters blindly, as it only needs to get a list of instances of this
* class, without knowing what they really drive. Second, it allows the physical
* model to not expose directly setters methods for its parameters. In order to be
* able to modify the parameter value, the algorithm <em>must</em> retrieve a
* parameter driver.
* </p>
* <p>
* As of versions 12.X and 13.X, it was possible to set up time-dependent values
* within a single {@code ParameterDriver}. This feature has been replaced by
* {@link ParameterDriversSequence} as of 14.0, which is simpler and also allows
* finer selection, making it possible to select only a subset of the parameters
* along a timeline. Starting with version 14.0, {@code ParameterDriver} instances
* only hold one value, which can have a restricted validity range.
* </p>
* @see ParameterObserver
* @author Luc Maisonobe
* @author Melina Vanel
* @since 8.0
*/
public class ParameterDriver {
/** Name of the parameter. */
private String name;
/** Reference value. */
private double referenceValue;
/** Scaling factor. */
private double scale;
/** Current value.
* @since 14.0
*/
private double value;
/** Minimum value. */
private double minValue;
/** Maximum value. */
private double maxValue;
/** Reference date.
* @since 9.0
*/
private AbsoluteDate referenceDate;
/** Validity interval.
* @since 14.0
*/
private TimeInterval validity;
/** Selection status.
* <p>
* Selection is used for estimated parameters in orbit determination,
* or to compute the Jacobian matrix in partial derivatives computation.
* </p>
*/
private boolean selected;
/** Observers observing this driver. */
private final List<ParameterObserver> observers;
/**
* Simple constructor.
* <p>
* At construction, the parameter is configured as <em>not</em> selected, the reference date is set to {@code null},
* the value is set to the {@code referenceValue}.
* </p>
* @param name name of the parameter
* @param referenceValue reference value of the parameter
* @param scale scaling factor to convert the parameters value to non-dimensional (typically set to the
* expected standard deviation of the parameter), it must be non-zero
* @param minValue minimum value allowed
* @param maxValue maximum value allowed
* @param validity validity interval
*/
public ParameterDriver(final String name,
final double referenceValue, final double scale,
final double minValue, final double maxValue,
final TimeInterval validity) {
if (FastMath.abs(scale) <= Precision.SAFE_MIN) {
throw new OrekitException(OrekitMessages.TOO_SMALL_SCALE_FOR_PARAMETER, name, scale);
}
this.name = name;
this.referenceValue = referenceValue;
this.scale = scale;
this.value = referenceValue;
this.minValue = minValue;
this.maxValue = maxValue;
this.validity = validity;
this.referenceDate = null;
this.selected = false;
this.observers = new ArrayList<>();
}
/** Add an observer for this driver.
* <p>
* The observer {@link ParameterObserver#valueChanged(double, ParameterDriver)
* valueChanged} method is called once automatically when the
* observer is added, and then called at each value change.
* </p>
* @param observer observer to add
*/
public void addObserver(final ParameterObserver observer) {
observers.add(observer);
}
/** Remove an observer.
* @param observer observer to remove
* @since 9.1
*/
public void removeObserver(final ParameterObserver observer) {
for (final Iterator<ParameterObserver> iterator = observers.iterator(); iterator.hasNext();) {
if (iterator.next() == observer) {
iterator.remove();
return;
}
}
}
/** Replace an observer.
* @param oldObserver observer to replace
* @param newObserver new observer to use
* @since 10.1
*/
public void replaceObserver(final ParameterObserver oldObserver, final ParameterObserver newObserver) {
for (int i = 0; i < observers.size(); ++i) {
if (observers.get(i) == oldObserver) {
observers.set(i, newObserver);
}
}
}
/** Get the observers for this driver.
* @return an unmodifiable view of the observers for this driver
* @since 9.1
*/
public List<ParameterObserver> getObservers() {
return Collections.unmodifiableList(observers);
}
/** Get parameter driver general name.
* @return name
*/
public String getName() {
return name;
}
/** Change the general name of this parameter driver.
* @param name new name
*/
public void setName(final String name) {
final String previousName = this.name;
this.name = name;
for (final ParameterObserver observer : observers) {
observer.nameChanged(previousName, this);
}
}
/** Get reference parameter value.
* @return reference parameter value
*/
public double getReferenceValue() {
return referenceValue;
}
/** Set reference parameter value.
* @since 9.3
* @param referenceValue the reference value to set.
*/
public void setReferenceValue(final double referenceValue) {
final double previousReferenceValue = this.referenceValue;
this.referenceValue = referenceValue;
for (final ParameterObserver observer : observers) {
observer.referenceValueChanged(previousReferenceValue, this);
}
}
/** Get minimum parameter value.
* @return minimum parameter value
*/
public double getMinValue() {
return minValue;
}
/** Set minimum parameter value.
* @since 9.3
* @param minValue the minimum value to set.
*/
public void setMinValue(final double minValue) {
// safety check
if (minValue > maxValue) {
throw new OrekitException(LocalizedCoreFormats.NUMBER_TOO_LARGE, minValue, maxValue);
}
if (value < minValue) {
// clip value to minimum
setValue(minValue);
}
final double previousMinValue = this.minValue;
this.minValue = minValue;
for (final ParameterObserver observer : observers) {
observer.minValueChanged(previousMinValue, this);
}
}
/** Get maximum parameter value.
* @return maximum parameter value
*/
public double getMaxValue() {
return maxValue;
}
/** Set maximum parameter value.
* @since 9.3
* @param maxValue the maximum value to set.
*/
public void setMaxValue(final double maxValue) {
// safety check
if (maxValue < minValue) {
throw new OrekitException(LocalizedCoreFormats.NUMBER_TOO_SMALL, maxValue, minValue);
}
if (value > maxValue) {
// clip value to maximum
setValue(maxValue);
}
final double previousMaxValue = this.maxValue;
this.maxValue = maxValue;
for (final ParameterObserver observer : observers) {
observer.maxValueChanged(previousMaxValue, this);
}
}
/** Get scale.
* @return scale
*/
public double getScale() {
return scale;
}
/** Set scale.
* @since 9.3
* @param scale the scale to set.
*/
public void setScale(final double scale) {
final double previousScale = this.scale;
this.scale = scale;
for (final ParameterObserver observer : observers) {
observer.scaleChanged(previousScale, this);
}
}
/** Get normalized value.
* <p>
* The normalized value is a non-dimensional value
* suitable for use as part of a vector in an optimization
* process. It is computed as {@code (current - reference)/scale}.
* </p>
* @return normalized value
*/
public double getNormalizedValue() {
return (value - referenceValue) / scale;
}
/** Set normalized value.
* <p>
* The normalized value is a non-dimensional value
* suitable for use as part of a vector in an optimization
* process. It is computed as {@code (current - reference)/scale}.
* </p>
* @param normalized value
*/
public void setNormalizedValue(final double normalized) {
setValue(referenceValue + scale * normalized);
}
/** Get current reference date.
* @return current reference date (null if it was never set)
* @since 9.0
*/
public AbsoluteDate getReferenceDate() {
return referenceDate;
}
/** Set reference date.
* @param newReferenceDate new reference date
* @since 9.0
*/
public void setReferenceDate(final AbsoluteDate newReferenceDate) {
final AbsoluteDate previousReferenceDate = getReferenceDate();
referenceDate = newReferenceDate;
for (final ParameterObserver observer : observers) {
observer.referenceDateChanged(previousReferenceDate, this);
}
}
/** Get current parameter value.
* @return current parameter value
*/
public double getValue() {
return value;
}
/** Get the value as a gradient.
* @param freeParameters total number of free parameters in the gradient
* @param indices indices of the differentiation parameters in derivatives computations
* @return value with derivatives
* @since 10.2
*/
public Gradient getValue(final int freeParameters, final Map<String, Integer> indices) {
final Integer index = indices.get(getName());
return (index == null) ?
Gradient.constant(freeParameters, getValue()) :
Gradient.variable(freeParameters, index, getValue());
}
/** Set parameter value.
* <p>
* If {@code newValue} is below {@link #getMinValue()}, it will
* be silently set to {@link #getMinValue()}. If {@code newValue} is
* above {@link #getMaxValue()}, it will be silently set to {@link
* #getMaxValue()}.
* </p>
* @param newValue new value to set
*/
public void setValue(final double newValue) {
final double previousValue = value;
value = FastMath.max(minValue, FastMath.min(maxValue, newValue));
for (final ParameterObserver observer : observers) {
observer.valueChanged(previousValue, this);
}
}
/** Get the validity interval.
* @return validity interval
* @since 14.0
*/
public TimeInterval getValidity() {
return validity;
}
/** Set the validity interval.
* @param validity validity interval
* @since 14.0
*/
public void setValidity(final TimeInterval validity) {
final TimeInterval previousValidity = getValidity();
this.validity = validity;
for (final ParameterObserver observer : observers) {
observer.validityChanged(previousValidity, this);
}
}
/** Configure a parameter selection status.
* <p>
* Selection is used for estimated parameters in orbit determination,
* or to compute the Jacobian matrix in partial derivatives computation.
* </p>
* @param selected if true the parameter is selected,
* otherwise it will be fixed
*/
public void setSelected(final boolean selected) {
final boolean previousSelection = isSelected();
this.selected = selected;
for (final ParameterObserver observer : observers) {
observer.selectionChanged(previousSelection, this);
}
}
/** Check if parameter is selected.
* <p>
* Selection is used for estimated parameters in orbit determination,
* or to compute the Jacobian matrix in partial derivatives computation.
* </p>
* @return true if parameter is selected, false if it is not
*/
public boolean isSelected() {
return selected;
}
/** Get a text representation of the parameter.
* @return text representation of the parameter, in the form name = value.
*/
public String toString() {
return name + " = " + value;
}
}