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

Class LambdaReranker<U,I>

java.lang.Object

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

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

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

Type Parameters:

U - type of the users

I - type of the items

All Implemented Interfaces:

Reranker<U,I>

public abstract class LambdaReranker<U,I>
extends GreedyReranker<U,I>

Linear combination re-ranker that combines the original score of the input recommendation and a novelty component.

Author:

Saúl Vargas (saul.vargas@uam.es), Pablo Castells (pablo.castells@uam.es)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	LambdaReranker.LambdaUserReranker User re-ranker for LambdaReranker.

Nested classes/interfaces inherited from class es.uam.eps.ir.ranksys.novdiv.reranking.GreedyReranker

GreedyReranker.GreedyUserReranker<U,I>

Field Summary

Fields

Modifier and Type	Field and Description
protected double	lambda Trade-off parameter of the linear combination.

Fields inherited from class es.uam.eps.ir.ranksys.novdiv.reranking.GreedyReranker

cutoff

Constructor Summary

Constructors

Constructor and Description
LambdaReranker(double lambda, int cutoff, boolean norm) Constructor.

Method Summary

Modifier and Type	Method and Description
protected abstract GreedyReranker.GreedyUserReranker<U,I>	getUserReranker(Recommendation<U,I> recommendation, int maxLength) Returns an instance of GreedyReranker.GreedyUserReranker that does the greedy selection.
int[]	rerankPermutation(Recommendation<U,I> recommendation, int maxLength) Returns the permutation that is applied to the input recommendation to generate the re-ranked recommendation.

Methods inherited from class es.uam.eps.ir.ranksys.novdiv.reranking.PermutationReranker

getBasePerm, permuteRecommendation, rerankRecommendation

Methods inherited from class java.lang.Object

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

Field Detail

lambda

protected final double lambda

Trade-off parameter of the linear combination.

Constructor Detail

LambdaReranker

public LambdaReranker(double lambda,
                      int cutoff,
                      boolean norm)

Constructor.

Parameters:

lambda - trade-off parameter of the linear combination

cutoff - how many items are re-ranked by the greedy selection.

norm - decides whether apply a normalization of the values of the component at each selection step

Method Detail

rerankPermutation

public int[] rerankPermutation(Recommendation<U,I> recommendation,
                               int maxLength)

Returns the permutation that is applied to the input recommendation to generate the re-ranked recommendation.

Overrides:

rerankPermutation in class GreedyReranker<U,I>

Parameters:

recommendation - input recommendation

maxLength - maximum length of the permutation

Returns:

permutation that encodes the re-ranking

getUserReranker

protected abstract GreedyReranker.GreedyUserReranker<U,I> getUserReranker(Recommendation<U,I> recommendation,
                                                                          int maxLength)

Description copied from class: GreedyReranker

Returns an instance of GreedyReranker.GreedyUserReranker that does the greedy selection.

Specified by:

getUserReranker in class GreedyReranker<U,I>

Parameters:

recommendation - input recommendation to be re-ranked

maxLength - maximum length of the resulting re-ranked recommendation

Returns:

the GreedyReranker.GreedyUserReranker that does the re-ranking