agi.foundation.geometry

(agi.foundation.core-2024r2.jar)

Class VectorDifferentiator

java.lang.Object

agi.foundation.infrastructure.DefinitionalObject

agi.foundation.geometry.Vector

agi.foundation.geometry.VectorDifferentiator

All Implemented Interfaces:

ICloneWithContext, IEnumerateDependencies, IEquatableDefinition, IFreezable, IServiceProvider

public class VectorDifferentiator
extends Vector

A Vector that can provide higher-order derivatives by finite-differencing another vector.

Constructor Summary

Constructors

Modifier	Constructor and Description
	VectorDifferentiator() Initializes a new instance.
protected	VectorDifferentiator(VectorDifferentiator existingInstance, CopyContext context) Initializes a new instance as a copy of an existing instance.
	VectorDifferentiator(Vector vector, double increment) Initializes a new instance.
	VectorDifferentiator(Vector vector, double increment, int derivativeToCompute) Initializes a new instance.

Method Summary

Modifier and Type	Method and Description
protected boolean	checkForSameDefinition(Vector other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
protected boolean	checkForSameDefinition(VectorDifferentiator other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
Object	clone(CopyContext context) Clones this object using the specified context.
protected int	computeCurrentDefinitionHashCode() Computes a hash code based on the current properties of this object.
void	enumerateDependencies(DependencyEnumerator enumerator) Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon.
int	getDerivativeToCompute() Gets the derivative to compute by finite-differencing.
Vector	getDifferentiatedVector() Gets the point whose highest order derivative is being differentiated
VectorEvaluator	getEvaluator(EvaluatorGroup group) Gets an evaluator that can be used to find the Motion<Cartesian> of this vector in its parent Axes at a given JulianDate.
double	getIncrement() Gets the increment used to calculate finite differences
void	setDerivativeToCompute(int value) Sets the derivative to compute by finite-differencing.
void	setDifferentiatedVector(Vector value) Sets the point whose highest order derivative is being differentiated
void	setIncrement(double value) Sets the increment used to calculate finite differences

Methods inherited from class agi.foundation.geometry.Vector

add, add, checkForSameDefinition, createVectorDerivative, cross, divide, divide, divide, divide, dot, getEvaluator, getScalarElement, getScalarElement, getService, multiply, multiply, multiply, multiply, multiply, multiply, subtract, subtract

Methods inherited from class agi.foundation.infrastructure.DefinitionalObject

areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, dictionaryItemsAreSameDefinition, freeze, freezeAggregatedObjects, getCollectionHashCode, getCollectionHashCode, getCollectionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDictionaryHashCode, getIsFrozen, isSameDefinition, throwIfFrozen

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

VectorDifferentiator

public VectorDifferentiator()

Initializes a new instance. The user must set both DifferentiatedVector (get / set) and Increment (get / set).

VectorDifferentiator

public VectorDifferentiator(Vector vector,
                            double increment)

Initializes a new instance.

Parameters:

vector - The vector to wrap and finite difference.

increment - The increment, in seconds, used to compute the finite difference.

VectorDifferentiator

public VectorDifferentiator(Vector vector,
                            double increment,
                            int derivativeToCompute)

Initializes a new instance.

Parameters:

vector - The vector to wrap and finite difference.

increment - The increment, in seconds, used to compute the finite difference.

derivativeToCompute - The derivative to compute, or 0 to specify that the next unavailable derivative should be computed. See the documentation for DerivativeToCompute (get / set) for more information.

VectorDifferentiator

protected VectorDifferentiator(@Nonnull
                               VectorDifferentiator existingInstance,
                               @Nonnull
                               CopyContext context)

Initializes a new instance as a copy of an existing instance.

See ICloneWithContext.clone(CopyContext) for more information about how to implement this constructor in a derived class.

Parameters:

existingInstance - The existing instance to copy.

context - A CopyContext that controls the depth of the copy.

Throws:

ArgumentNullException - Thrown when existingInstance or context is null.

Method Detail

clone

public Object clone(CopyContext context)

Clones this object using the specified context.

This method should be implemented to call a copy constructor on the class of the object being cloned. The copy constructor should take the CopyContext as a parameter in addition to the existing instance to copy. The copy constructor should first call CopyContext.addObjectMapping(T, T) to identify the newly constructed instance as a copy of the existing instance. It should then copy all fields, using CopyContext.updateReference(T) to copy any reference fields.

A typical implementation of ICloneWithContext:

public static class MyClass implements ICloneWithContext {
    public MyClass(MyClass existingInstance, CopyContext context) {
        context.addObjectMapping(existingInstance, this);
        someReference = context.updateReference(existingInstance.someReference);
    }

    @Override
    public final Object clone(CopyContext context) {
        return new MyClass(this, context);
    }

    private Object someReference;
}

In general, all fields that are reference types should be copied with a call to CopyContext.updateReference(T). There are a couple of exceptions:

1. Fields that are aggregate parts of the object should always be copied. A referenced object is an aggregate if properties or methods on the object being copied can modify the externally-visible value of the referenced object.
2. If the semantics of the referenced object require that it have a single parent, owner, context, etc., and the object being copied is that parent, owner, or context, then the referenced object should always be copied.

If one of these exceptions applies, the CopyContext should be given an opportunity to update the reference before the reference is copied explicitly. Use CopyContext.updateReference(T) to update the reference. If CopyContext.updateReference(T) returns the original object, indicating that the context does not have a replacement registered, then copy the object manually by invoking a Clone method, a copy constructor, or by manually constructing a new instance and copying the values.

alwaysCopy = context.updateReference(existingInstance.alwaysCopy);
if (existingInstance.alwaysCopy != null && alwaysCopy == existingInstance.alwaysCopy) {
    alwaysCopy = (AlwaysCopy) existingInstance.alwaysCopy.clone(context);
}

If you are implementing an evaluator (a class that implements IEvaluator), the IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) method shares some responsibilities with the copy context constructor. Code duplication can be avoided by doing the following:

1. For references to other evaluators ONLY, simply assign the reference in the constructor instead of calling CopyContext.updateReference(T). You should still call CopyContext.updateReference(T) on any references to non-evaluators.
2. Call IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as the last line in the constructor and pass it the same CopyContext passed to the constructor.
3. Implement IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as normal. See the reference documentation for IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) for more information on implementing that method.

public MyClass(MyClass existingInstance, CopyContext context) {
    super(existingInstance, context);
    someReference = context.updateReference(existingInstance.someReference);
    evaluatorReference = existingInstance.evaluatorReference;
    updateEvaluatorReferences(context);
}

@Override
public void updateEvaluatorReferences(CopyContext context) {
    evaluatorReference = context.updateReference(evaluatorReference);
}

@Override
public Object clone(CopyContext context) {
    return new MyClass(this, context);
}

private Object someReference;
private IEvaluator evaluatorReference;

Specified by:

clone in interface ICloneWithContext

Specified by:

clone in class DefinitionalObject

Parameters:

context - The context to use to perform the copy.

Returns:

A new instance which is a copy of this object.

checkForSameDefinition

protected final boolean checkForSameDefinition(Vector other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Specified by:

checkForSameDefinition in class Vector

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

checkForSameDefinition

protected boolean checkForSameDefinition(VectorDifferentiator other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

computeCurrentDefinitionHashCode

protected int computeCurrentDefinitionHashCode()

Computes a hash code based on the current properties of this object. Derived classes MUST override this method and compute a hash code that combines: a unique hash code seed, the base implementation result, and the hash codes of all new fields introduced by the derived class which are used in the VectorDifferentiator.checkForSameDefinition(agi.foundation.geometry.Vector) method.

Overrides:

computeCurrentDefinitionHashCode in class Vector

Returns:

The computed hash code.

enumerateDependencies

public void enumerateDependencies(DependencyEnumerator enumerator)

Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon. Derived classes which contain additional dependencies MUST override this method, call the base implementation, and enumerate dependencies introduced by the derived class.

Specified by:

enumerateDependencies in interface IEnumerateDependencies

Overrides:

enumerateDependencies in class DefinitionalObject

Parameters:

enumerator - The enumerator that is informed of the dependencies of this object.

getDifferentiatedVector

public final Vector getDifferentiatedVector()

Gets the point whose highest order derivative is being differentiated

setDifferentiatedVector

public final void setDifferentiatedVector(Vector value)

Sets the point whose highest order derivative is being differentiated

getIncrement

public final double getIncrement()

Gets the increment used to calculate finite differences

setIncrement

public final void setIncrement(double value)

Sets the increment used to calculate finite differences

getDerivativeToCompute

public final int getDerivativeToCompute()

Gets the derivative to compute by finite-differencing. For example, a value of 1 for this property indicates that the first derivative (or vector rate) should be computed. A value of 0 (the default) will cause the first derivative that is not supplied directly by DifferentiatedVector (get / set) to be computed.

A given derivative can only be computed if the next lower order derivative exists. For example, acceleration can only be computed if velocity is already supplied by DifferentiatedVector (get / set). If the requested derivative cannot be computed, the highest possible derivative will be computed instead.

setDerivativeToCompute

public final void setDerivativeToCompute(int value)

Sets the derivative to compute by finite-differencing. For example, a value of 1 for this property indicates that the first derivative (or vector rate) should be computed. A value of 0 (the default) will cause the first derivative that is not supplied directly by DifferentiatedVector (get / set) to be computed.

A given derivative can only be computed if the next lower order derivative exists. For example, acceleration can only be computed if velocity is already supplied by DifferentiatedVector (get / set). If the requested derivative cannot be computed, the highest possible derivative will be computed instead.

getEvaluator

public VectorEvaluator getEvaluator(EvaluatorGroup group)

Gets an evaluator that can be used to find the Motion<Cartesian> of this vector in its parent Axes at a given JulianDate. This evaluator can represent derivatives of the given DifferentiatedVector (get / set) using finite difference.

Specified by:

getEvaluator in class Vector

Parameters:

group - The group with which to associate the new evaluator. By grouping evaluators that are often evaluated at the same Julian dates, common computations can be performed only once for the entire group instead of multiple times for each evaluator.

Returns:

An evaluator for this vector.

Throws:

ArgumentNullException - Thrown if group is null.

PropertyInvalidException - Thrown if DifferentiatedVector (get / set) is null, or if Increment (get / set) is zero, or if DerivativeToCompute (get / set) is not positive or zero.