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https://issues.apache.org/jira/browse/NUMBERS-176?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Alex Herbert resolved NUMBERS-176.
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Fix Version/s: 1.1
Resolution: Implemented
Added in commit
23ba4f8ea6109c9bac7b4ec43e17dcaaed358bd9
> ContinuedFraction to delegate to GeneralizedContinuedFraction
> -------------------------------------------------------------
>
> Key: NUMBERS-176
> URL: https://issues.apache.org/jira/browse/NUMBERS-176
> Project: Commons Numbers
> Issue Type: Improvement
> Components: fraction
> Affects Versions: 1.1
> Reporter: Alex Herbert
> Priority: Trivial
> Fix For: 1.1
>
>
> The ContinuedFraction class evaluates using the same algorithm as the
> GeneralizedContinuedFraction. These should use the same code to eliminate
> duplication.
> The GeneralizedContinuedFraction has the latest version of the algorithm with
> a bug fix for detecting invalid update steps and increased support for very
> small convergence epsilon (see NUMBERS-175).
> The simple approach is to call the GeneralizedContinuedFraction by creating a
> generator from the ContinuedFraction and the argument x:
> {code:java}
> public double evaluate(double x, double epsilon, int maxIterations) {
> // Delegate to GeneralizedContinuedFraction
> // Get the first coefficient
> final double b0 = getB(0, x);
> // Generate coefficients from (a1,b1)
> final Supplier<Coefficient> gen = new Supplier<Coefficient>() {
> private int n;
> @Override
> public Coefficient get() {
> n++;
> final double a = getA(n, x);
> final double b = getB(n, x);
> return Coefficient.of(a, b);
> }
> };
> // Invoke appropriate method based on magnitude of first term
> if (Math.abs(b0) < SMALL) {
> return GeneralizedContinuedFraction.value(b0, gen, epsilon,
> maxIterations);
> }
> return GeneralizedContinuedFraction.evaluate(b0, gen, epsilon,
> maxIterations);
> }
> {code}
> This will only evaluate each used coefficient once. It requires exposure of
> the GeneralizedContinuedFraction.evaluate method at the package level.
> The threshold for small values and default for iterations can be exposed as
> package private from GeneralizedContinuedFraction. This ensures the method
> calls the appropriate evaluation method based on the magnitude of the first
> term b0 with the same defaults.
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