org.databene.benerator.primitive.number
Class RecurrenceRelationNumberGenerator<E extends java.lang.Number>

java.lang.Object
  org.databene.benerator.util.AbstractGenerator<E>
      org.databene.benerator.primitive.number.AbstractNumberGenerator<E>
          org.databene.benerator.primitive.number.RecurrenceRelationNumberGenerator<E>

All Implemented Interfaces:

java.io.Closeable, Generator<E>, org.databene.commons.Resettable, org.databene.commons.ThreadAware

Direct Known Subclasses:

FibonacciLongGenerator, PadovanLongGenerator

public abstract class RecurrenceRelationNumberGenerator<E extends java.lang.Number>
extends AbstractNumberGenerator<E>

Parent class for Number Generators that calculate numbers recursively. Child classes can define recursive sequences easily by defining a depth and implementing the methods a0(int) and aN().

The recursion depth needs to be specified in the constructor call, a0(int) needs to return the predefined initial value(s) of the sequence (f0, f1, ...) and aN() implements the recursion (fN = f(f(n-1), f(n-2), ...).

Example: The Fibonacci sequence is defined recursively by

• F(0) = 1
• F(1) = 1
• F(n) = F(n-1) + F(n-2)

For a Generator of Long values, this translates to an implementation with

depth = 2
  
 protected Long aN() {
     return aN(-1) + aN(-2);
 }

 protected Long a0(int n) {
     return (n == 0 ? 0L : 1L);
 }
 

Have a look at the FibonacciLongGenerator source code for the complete implementation.

Created: 13.10.2009 19:07:27

Since:

0.6.0

Author:

Volker Bergmann

Field Summary

Fields inherited from class org.databene.benerator.primitive.number.AbstractNumberGenerator

generatedType, max, min, precision

Fields inherited from class org.databene.benerator.util.AbstractGenerator

context, state

Constructor Summary

RecurrenceRelationNumberGenerator(java.lang.Class<E> targetType, int depth, E min, E max)

Method Summary

protected abstract E	a0(int n) Must be implemented by child classes to return the seed values of the recurrence relation.
protected abstract E	aN() Must be implemented by child classes to implement the recurrence relation.
protected E	aN(int offset) Provides the most recent calculated values.
protected E	calculateNext()
void	close() See Generator.close()
E	generate() See Generator.generate()
int	getDepth()
int	getN()
void	init(GeneratorContext context)
void	reset() See Resettable.reset()
protected void	resetMembers()

Methods inherited from class org.databene.benerator.primitive.number.AbstractNumberGenerator

getGeneratedType, getMax, getMin, getPrecision, isParallelizable, isThreadSafe, setMax, setMin, setPrecision

Methods inherited from class org.databene.benerator.util.AbstractGenerator

assertInitialized, assertNotInitialized, toString, wasInitialized

Methods inherited from class java.lang.Object

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

Constructor Detail

RecurrenceRelationNumberGenerator

public RecurrenceRelationNumberGenerator(java.lang.Class<E> targetType,
                                         int depth,
                                         E min,
                                         E max)

Method Detail

getDepth

public int getDepth()

getN

public int getN()

init

public void init(GeneratorContext context)

Specified by:

init in interface Generator<E extends java.lang.Number>

Overrides:

init in class AbstractNumberGenerator<E extends java.lang.Number>

generate

public E generate()

See Generator.generate()

reset

public void reset()

See Resettable.reset()

Specified by:

reset in interface org.databene.commons.Resettable

Overrides:

reset in class AbstractGenerator<E extends java.lang.Number>

close

public void close()

See Generator.close()

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface Generator<E extends java.lang.Number>

Overrides:

close in class AbstractGenerator<E extends java.lang.Number>

a0

protected abstract E a0(int n)

Must be implemented by child classes to return the seed values of the recurrence relation. These are the initial values which are defined as constants (a(0)..a(depth-1)).

aN

protected abstract E aN()

Must be implemented by child classes to implement the recurrence relation. It needs to use the aN(int) method to retrieve the most recent calculated values.

aN

protected final E aN(int offset)

Provides the most recent calculated values. The index is the relative index, -1 stands for a(N-1).

resetMembers

protected void resetMembers()

calculateNext

protected E calculateNext()