gov.sandia.cognition.math

Class LentzMethod

java.lang.Object

gov.sandia.cognition.util.AbstractCloneableSerializable

gov.sandia.cognition.algorithm.AbstractIterativeAlgorithm

gov.sandia.cognition.algorithm.AbstractAnytimeAlgorithm<java.lang.Double>

gov.sandia.cognition.math.LentzMethod

All Implemented Interfaces:

AnytimeAlgorithm<java.lang.Double>, IterativeAlgorithm, StoppableAlgorithm, CloneableSerializable, java.io.Serializable, java.lang.Cloneable

@PublicationReference(author={"William H. Press","Saul A. Teukolsky","William T. Vetterling","Brian P. Flannery"},
                      title="Numerical Recipes in C, Second Edition",
                      type=Book,
                      year=1992,
                      pages={169,171},
                      url="http://www.nrbook.com/a/bookcpdf.php")
public class LentzMethod
extends AbstractAnytimeAlgorithm<java.lang.Double>

This class implements Lentz's method for evaluating continued fractions. This is an iterative, approximate approach that has good convergence. By specifying the fraction as f(x) = b0 + a1/(b1+a1/(b2+a3/(b3+...))). Each iteration, we take the (a,b) coefficients and improve the approximation of f(x) and terminate after too many iterations or convergence.

Since:

2.1

Author:

Kevin R. Dixon

See Also:

Serialized Form

Field Summary

Fields inherited from class gov.sandia.cognition.algorithm.AbstractAnytimeAlgorithm

maxIterations

Fields inherited from class gov.sandia.cognition.algorithm.AbstractIterativeAlgorithm

DEFAULT_ITERATION, iteration

Constructor Summary

Constructors

Constructor and Description
LentzMethod() Creates a new instance of LentzMethod
LentzMethod(int maxIterations, double tolerance, double minDenominator) Creates a new instance of LentzMethod

Method Summary

Modifier and Type	Method and Description
double	getFractionValue() Getter for fractionValue
boolean	getKeepGoing() Getter for keepGoing
double	getMinDenominator() Getter for minDenominator
java.lang.Double	getResult() Gets the current result of the algorithm.
double	getTolerance() Getter for tolerance
boolean	initializeAlgorithm(double b0) Initializes Lentz's method using the given values
boolean	iterate(double a, double b) Step of Lentz's iteration
protected void	setFractionValue(double fractionValue) Setter for fractionValue
void	setMinDenominator(double minDenominator) Setter for minDenominator
void	setTolerance(double tolerance) Setter for tolerance
void	stop() Requests that the algorithm stop at the next appropriate point.

Methods inherited from class gov.sandia.cognition.algorithm.AbstractAnytimeAlgorithm

getMaxIterations, isResultValid, setMaxIterations

Methods inherited from class gov.sandia.cognition.algorithm.AbstractIterativeAlgorithm

addIterativeAlgorithmListener, clone, fireAlgorithmEnded, fireAlgorithmStarted, fireStepEnded, fireStepStarted, getIteration, getListeners, removeIterativeAlgorithmListener, setIteration, setListeners

Methods inherited from class java.lang.Object

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

Methods inherited from interface gov.sandia.cognition.algorithm.IterativeAlgorithm

addIterativeAlgorithmListener, getIteration, removeIterativeAlgorithmListener

Constructor Detail

LentzMethod

public LentzMethod()

Creates a new instance of LentzMethod

LentzMethod

public LentzMethod(int maxIterations,
                   double tolerance,
                   double minDenominator)

Creates a new instance of LentzMethod

Parameters:

maxIterations - Maximum number of iterations before stopping

tolerance - Tolerance of the algorithm for convergence

minDenominator - Value to keep denominators from equaling 0.0

Method Detail

initializeAlgorithm

public boolean initializeAlgorithm(double b0)

Initializes Lentz's method using the given values

Parameters:

b0 - Initial "b" coefficient of the continued fraction

Returns:

keep going flag

iterate

public boolean iterate(double a,
                       double b)

Step of Lentz's iteration

Parameters:

a - coefficient "a" from the next recursion of the continued fraction

b - coefficient "b" from the next recursion of the continued fraction

Returns:

keep going flag

getTolerance

public double getTolerance()

Getter for tolerance

Returns:

Tolerance of the algorithm for convergence

setTolerance

public void setTolerance(double tolerance)

Setter for tolerance

Parameters:

tolerance - Tolerance of the algorithm for convergence

getMinDenominator

public double getMinDenominator()

Getter for minDenominator

Returns:

The minimum denominator.

setMinDenominator

public void setMinDenominator(double minDenominator)

Setter for minDenominator

Parameters:

minDenominator - Value to keep denominators from equaling 0.0

getResult

public java.lang.Double getResult()

Description copied from interface: AnytimeAlgorithm

Gets the current result of the algorithm.

Returns:

Current result of the algorithm.

stop

public void stop()

Description copied from interface: StoppableAlgorithm

Requests that the algorithm stop at the next appropriate point. The stopping point is determined by the algorithm. The algorithm should try to balance between stopping as soon as possible and leaving the results in some consistent state.

getKeepGoing

public boolean getKeepGoing()

Getter for keepGoing

Returns:

Flag to keep going or stop

getFractionValue

public double getFractionValue()

Getter for fractionValue

Returns:

Running (intermediate) value of the fraction value

setFractionValue

protected void setFractionValue(double fractionValue)

Setter for fractionValue

Parameters:

fractionValue - Running (intermediate) value of the fraction value