es.uam.eps.ir.ranksys.novdiv.reranking

Class GreedyReranker.GreedyUserReranker<U,I>

java.lang.Object

es.uam.eps.ir.ranksys.novdiv.reranking.GreedyReranker.GreedyUserReranker<U,I>

Type Parameters:

U - type of the users

I - type of the items

Direct Known Subclasses:

LambdaReranker.LambdaUserReranker

Enclosing class:

GreedyReranker<U,I>

protected abstract class GreedyReranker.GreedyUserReranker<U,I>
extends Object

Re-ranker of a single recommendation.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	maxLength maximum length of the re-ranked recommendation
protected Recommendation<U,I>	recommendation input recommendation

Constructor Summary

Constructors

Constructor and Description
GreedyUserReranker(Recommendation<U,I> recommendation, int maxLength) Constructor

Method Summary

Modifier and Type	Method and Description
int[]	rerankPermutation() Returns the permutation to obtain the re-ranking
protected int	selectItem(it.unimi.dsi.fastutil.ints.IntSortedSet remainingI, List<Tuple2od<I>> list) Selects the next element of the permutation that maximizes the objective function.
protected abstract void	update(Tuple2od<I> bestItemValue) Updates the value of the objective function after a selection.
protected abstract double	value(Tuple2od<I> itemValue) Objective function that drives the greedy selection.

Methods inherited from class java.lang.Object

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

Field Detail

recommendation

protected final Recommendation<U,I> recommendation

input recommendation

maxLength

protected final int maxLength

maximum length of the re-ranked recommendation

Constructor Detail

GreedyUserReranker

public GreedyUserReranker(Recommendation<U,I> recommendation,
                          int maxLength)

Constructor

Parameters:

recommendation - input recommendation

maxLength - maximum length of the re-ranked recommendation

Method Detail

rerankPermutation

public int[] rerankPermutation()

Returns the permutation to obtain the re-ranking

Returns:

permutation to obtain the re-ranking

selectItem

protected int selectItem(it.unimi.dsi.fastutil.ints.IntSortedSet remainingI,
                         List<Tuple2od<I>> list)

Selects the next element of the permutation that maximizes the objective function.

Parameters:

remainingI - positions of the original recommendation that have not been selected yet.

list - the list of item-score pairs of the input recommendation

Returns:

the next element of the permutation that maximizes the objective function.

value

protected abstract double value(Tuple2od<I> itemValue)

Objective function that drives the greedy selection.

Parameters:

itemValue - item-score pair of the input recommendation.

Returns:

value of the function with the given item-score pair.

update

protected abstract void update(Tuple2od<I> bestItemValue)

Updates the value of the objective function after a selection.

Parameters:

bestItemValue - item-score pair that has been selected to be added to the re-ranking