gov.nasa.jpf.util

Class RandomPermutationGenerator

java.lang.Object

gov.nasa.jpf.util.PermutationGenerator

gov.nasa.jpf.util.RandomPermutationGenerator

Direct Known Subclasses:

UniqueRandomPermGenerator

public class RandomPermutationGenerator
extends PermutationGenerator

a permutation generator that uses the Fisher-Yates shuffle (Durstenfeld, R. (July 1964). "Algorithm 235: Random permutation". Communications of the ACM 7 (7): 420) use this if TotalPermutations would be too large and PairPermutations not enough

Field Summary

Fields

Modifier and Type	Field and Description
protected int[]	orig
protected java.util.Random	rand
protected int	seed

Fields inherited from class gov.nasa.jpf.util.PermutationGenerator

nElements, nGenerated, nPermutations, permutation

Constructor Summary

Constructors

Constructor and Description
RandomPermutationGenerator(int nElements, int nPermutations, int seed)

Method Summary

Modifier and Type	Method and Description
protected long	computeNumberOfPermutations()
int[]	next() return the next permutation or throw a NoSuchElementException if there is none.
void	reset()

Methods inherited from class gov.nasa.jpf.util.PermutationGenerator

getNumberOfGeneratedPermutations, getNumberOfPermutations, hasNext, initPermutations, printOn, printOn

Methods inherited from class java.lang.Object

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

Field Detail

seed

protected int seed

rand

protected java.util.Random rand

orig

protected int[] orig

Constructor Detail

RandomPermutationGenerator

public RandomPermutationGenerator(int nElements,
                                  int nPermutations,
                                  int seed)

Method Detail

computeNumberOfPermutations

protected long computeNumberOfPermutations()

Specified by:

computeNumberOfPermutations in class PermutationGenerator

reset

public void reset()

Specified by:

reset in class PermutationGenerator

next

public int[] next()

Description copied from class: PermutationGenerator

return the next permutation or throw a NoSuchElementException if there is none. NOTE - this does not guarantee to return a different object on each call, i.e. the caller has to clone if the result is stored directly

Specified by:

next in class PermutationGenerator