public class RungeKuttaAlgorithm extends Object implements IThreadAware
The basic RungeKutta integration algorithm used by the integrators, it's Butcher Tableau, and the derivative information computed during integration.
y[n+1] = y[n] + h * Sum(i=0 to s){ b[i]*k[i] }
k[i] = f(t[n] + c[i]*h, y[n] + Sum(j=0 to i1){ a[i,j] * k[j] } )
Modifier  Constructor and Description 


RungeKuttaAlgorithm(double[] stages,
double[] weights,
double[][] coefficients)
Initializes a new instance of a RungeKutta algorithm with the given Butcher Tableau.

protected 
RungeKuttaAlgorithm(RungeKuttaAlgorithm existingInstance,
CopyContext context)
Initializes a new instance as a copy of an existing instance.

Modifier and Type  Method and Description 

Object 
clone(CopyContext context)
Clones this object using the specified context.

double[][] 
getCoefficients()
Gets the coefficients "a".

DependentVariableDerivatives 
getDerivativeFunction()
Gets the delegate which defines the first order differential equation representing the
derivative of the dependent variables as a function of independent variable and dependent variables.

double[][] 
getDerivatives()
Gets the derivative information used in the algorithm.

boolean 
getIsThreadSafe()
Gets a value indicating whether the methods on this instance are safe to call from
multiple threads simultaneously.

int 
getNumberOfStages()
Gets the total number of stages in this instance of the RungeKutta integrator.

double[] 
getStages()
Gets the coefficients "c".

double[] 
getWeights()
Gets the coefficients "b".

protected double[] 
getWorkingArray()

void 
initialize(int dimension,
DependentVariableDerivatives function)

void 
integrate(double step,
double initialIndependentVariableValue,
double[] initialDependentVariableValues,
double[] finalDependentVariableValues)
Compute an integration step and update the final dependent variables and store the
Derivatives (get ). 
public RungeKuttaAlgorithm(@Nonnull double[] stages, @Nonnull double[] weights, @Nonnull double[][] coefficients)
Initializes a new instance of a RungeKutta algorithm with the given Butcher Tableau.
y[n+1] = y[n] + h * Sum(i=0 to s){ b[i]*k[i] }
k[i] = f(t[n] + c[i]*h, y[n] + Sum(j=0 to i1){ a[i,j] * k[j] } )
stages
 The coefficients "c".
These represent the factors multiplying the step size by which to advance the independent variable at each stage.weights
 The coefficients "b".
These represent the coefficients of the "k" stages summed together to represent the slope.coefficients
 The coefficients "a".
These represent the factors multiplying the derivatives to provide the intermediate state information.protected RungeKuttaAlgorithm(@Nonnull RungeKuttaAlgorithm existingInstance, @Nonnull CopyContext context)
See ICloneWithContext.clone(CopyContext)
for more information about how to implement this constructor
in a derived class.
existingInstance
 The existing instance to copy.context
 A CopyContext
that controls the depth of the copy.ArgumentNullException
 Thrown when existingInstance
or context
is null
.public final Object clone(CopyContext 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:
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:
CopyContext.updateReference(T)
. You should still call CopyContext.updateReference(T)
on any references to
nonevaluators.
IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext)
as the last line in the constructor and pass it the
same CopyContext
passed to the constructor.
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;
clone
in interface ICloneWithContext
context
 The context to use to perform the copy.public final boolean getIsThreadSafe()
If this property is true
, all methods and properties are guaranteed to be thread safe.
Conceptually, an object that returns true
for this method acts as if there is a lock
protecting each method and property such that only one thread at a time can be inside any method or
property in the class. In reality, such locks are generally not used and are in fact discouraged. However,
the user must not experience any exceptions or inconsistent behavior that would not be experienced if such
locks were used.
If this property is false
, the behavior when using this class from multiple threads
simultaneously is undefined and may include inconsistent results and exceptions. Clients wishing to use
multiple threads should call CopyForAnotherThread.copy(T)
to get a separate instance of the
object for each thread.
getIsThreadSafe
in interface IThreadAware
public final int getNumberOfStages()
public final double[] getStages()
public final double[] getWeights()
public final double[][] getCoefficients()
public final double[][] getDerivatives()
protected final double[] getWorkingArray()
public final DependentVariableDerivatives getDerivativeFunction()
public final void initialize(int dimension, DependentVariableDerivatives function)
DerivativeFunction
(get
/ set
) and the working arrays used during integration.dimension
 The dimension of the state.function
 The first order differential function representing the derivative of the dependent variables
as a function of independent variable and dependent variables.public final void integrate(double step, double initialIndependentVariableValue, double[] initialDependentVariableValues, double[] finalDependentVariableValues)
Derivatives
(get
).step
 The size of the step "h" to take.initialIndependentVariableValue
 The initial independent variable value "t[n]".initialDependentVariableValues
 The initial dependent variable value "y[n]".finalDependentVariableValues
 The final dependent variable value "y[n+1]" which will be updated.