gov.nasa.jpf.util

Class PairPermutationGenerator

java.lang.Object

gov.nasa.jpf.util.PermutationGenerator

gov.nasa.jpf.util.PairPermutationGenerator

public class PairPermutationGenerator
extends PermutationGenerator

a generator for pair-wise permutations, which only considers permutations for each pair of elements, regardless of position. This reduces the number of generated permutations from N! to sum(i=1..N){N-i} + 1. This can be used to test order dependencies between two concurrent entities (threads, state machines etc), based on the same assumptions that are used in pair-wise testing

Field Summary

Fields

Modifier and Type	Field and Description
protected int	i
protected int	j

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

nElements, nGenerated, nPermutations, permutation

Constructor Summary

Constructors

Constructor and Description
PairPermutationGenerator(int nElements)

Method Summary

Modifier and Type	Method and Description
protected long	computeNumberOfPermutations()
static long	computeNumberOfPermutations(int n)
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

i

protected int i

j

protected int j

Constructor Detail

PairPermutationGenerator

public PairPermutationGenerator(int nElements)

Method Detail

reset

public void reset()

Specified by:

reset in class PermutationGenerator

computeNumberOfPermutations

public static long computeNumberOfPermutations(int n)

computeNumberOfPermutations

protected long computeNumberOfPermutations()

Specified by:

computeNumberOfPermutations 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