net.sf.tweety.commons.util

Class RandomSubsetIterator<T>

java.lang.Object

net.sf.tweety.commons.util.SubsetIterator<T>

net.sf.tweety.commons.util.RandomSubsetIterator<T>

Type Parameters:

T - The element class which is iterated.

All Implemented Interfaces:

java.util.Iterator<java.util.Set<T>>

public class RandomSubsetIterator<T>
extends SubsetIterator<T>

Iterates over all subsets of a given sets in a random order.

Author:

Matthias Thimm

Field Summary

Fields

Modifier and Type	Field and Description
private double	allSubsets Only used when avoidDuplicats is set to true.
private boolean	avoidDuplicates Whether to avoid duplicates in the iteration.
private long	generatedSubsets Only used when avoidDuplicats is set to true.
private java.util.Random	random The random number generator.
private java.util.List<T>	set The set over which subsets are iterated.
private boolean	switched Only used when avoidDuplicats is set to true.
private java.util.Set<java.util.BitSet>	temp Only used when avoidDuplicats is set to true.

Constructor Summary

Constructors

Constructor and Description
RandomSubsetIterator(java.util.Set<T> set, boolean avoidDuplicates) Creates a new subset iterator for the given set.

Method Summary

Modifier and Type	Method and Description
private java.util.BitSet	generate(int length, boolean checkForDuplicates) Generates a new bit set of the given length.
private java.util.BitSet	generateRandomly(int length) Generates a random bit set of the given length.
boolean	hasNext()
private void	increment(java.util.BitSet bitSet) Increments the given bit set
java.util.Set<T>	next()

Methods inherited from class net.sf.tweety.commons.util.SubsetIterator

getSet, remove

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

forEachRemaining

Field Detail

set

private java.util.List<T> set

The set over which subsets are iterated.

avoidDuplicates

private boolean avoidDuplicates

Whether to avoid duplicates in the iteration.

random

private java.util.Random random

The random number generator.

temp

private java.util.Set<java.util.BitSet> temp

Only used when avoidDuplicats is set to true. Then this set contains all (representations of) subsets already generated (if those are less than half the number of all subsets) or the subsets not generated yet (otherwise).

generatedSubsets

private long generatedSubsets

Only used when avoidDuplicats is set to true. The number of already generated subsets.

allSubsets

private double allSubsets

Only used when avoidDuplicats is set to true. The number of all subsets.

switched

private boolean switched

Only used when avoidDuplicats is set to true. Whether the mode of using this.temp has been switched.

Constructor Detail

RandomSubsetIterator

public RandomSubsetIterator(java.util.Set<T> set,
                            boolean avoidDuplicates)

Creates a new subset iterator for the given set.

Parameters:

set - some set.

avoidDuplicates - whether to avoid duplicates in the iteration. NOTE: setting this value to true might increase computation time and needed space drastically.

Method Detail

hasNext

public boolean hasNext()

Specified by:

hasNext in interface java.util.Iterator<java.util.Set<T>>

Specified by:

hasNext in class SubsetIterator<T>

next

public java.util.Set<T> next()

Specified by:

next in interface java.util.Iterator<java.util.Set<T>>

Specified by:

next in class SubsetIterator<T>

increment

private void increment(java.util.BitSet bitSet)

Increments the given bit set

Parameters:

bitSet - some bit set.

generate

private java.util.BitSet generate(int length,
                                  boolean checkForDuplicates)

Generates a new bit set of the given length. If checkForDuplicates is true then the all bit sets in this.temp are regarded as already being generated and the new one will be different from all of those. Furthermore, the new bit set is added to this.temp. If checkForDuplicates is false, the new bit set will be chosen from this.temp and removed there.

Parameters:

length - the length of the bit set.

checkForDuplicates - whether to check for duplicates (see above).

Returns:

a bit set.

generateRandomly

private java.util.BitSet generateRandomly(int length)

Generates a random bit set of the given length.

Parameters:

length - some length.

Returns:

a random bit set.