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

Class PermutationReranker<U,I>

java.lang.Object

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

Type Parameters:

U - type of the users

I - type of the items

All Implemented Interfaces:

Reranker<U,I>

Direct Known Subclasses:

DitheringReranker, GreedyReranker, ItemNoveltyReranker, NullReranker, RandomReranker

public abstract class PermutationReranker<U,I>
extends Object
implements Reranker<U,I>

Abstract re-ranker whose output is a permutation of the input recommendation. Convenient for storing the minimum required information.

Author:

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

Constructor Summary

Constructors

Constructor and Description
PermutationReranker()

Method Summary

Modifier and Type	Method and Description
protected static int[]	getBasePerm(int n) Returns a null permutation, that is, an array with values 0..(N-1).
static <U,I> Recommendation<U,I>	permuteRecommendation(Recommendation<U,I> recommendation, int[] perm) Applies a permutation to re-rank a recommendation.
abstract int[]	rerankPermutation(Recommendation<U,I> recommendation, int maxLength) Returns the permutation that is applied to the input recommendation to generate the re-ranked recommendation.
Recommendation<U,I>	rerankRecommendation(Recommendation<U,I> recommendation, int maxLength) Re-ranks a recommendation.

Methods inherited from class java.lang.Object

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

Constructor Detail

PermutationReranker

public PermutationReranker()

Method Detail

rerankPermutation

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

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

Parameters:

recommendation - input recommendation

maxLength - maximum length of the permutation

Returns:

permutation that encodes the re-ranking

rerankRecommendation

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

Description copied from interface: Reranker

Re-ranks a recommendation.

Specified by:

rerankRecommendation in interface Reranker<U,I>

Parameters:

recommendation - recommendation to be re-ranked

maxLength - maximum length of the re-ranking

Returns:

a recommendation that is a re-ranking of the input one

permuteRecommendation

public static <U,I> Recommendation<U,I> permuteRecommendation(Recommendation<U,I> recommendation,
                                                              int[] perm)

Applies a permutation to re-rank a recommendation.

Type Parameters:

U - type of the users

I - type of the items

Parameters:

recommendation - input recommendation

perm - permutation

Returns:

re-ranked recommendation according to the permutation

getBasePerm

protected static int[] getBasePerm(int n)

Returns a null permutation, that is, an array with values 0..(N-1).

Parameters:

n - size of the permutation

Returns:

null permutation