Package es.uam.eps.ir.relison.links.recommendation.reranking.global.local

Class LocalGreedyReranker<U,​I>

java.lang.Object
es.uam.eps.ir.relison.links.recommendation.reranking.global.local.LocalReranker<U,​I>
es.uam.eps.ir.relison.links.recommendation.reranking.global.local.LocalGreedyReranker<U,​I>
Type Parameters:
U - type of the users.
I - type of the items.
All Implemented Interfaces:
GlobalReranker<U,​I>
Direct Known Subclasses:
LocalLambdaReranker
public abstract class LocalGreedyReranker<U,​I>
extends LocalReranker<U,​I>
Generalization of greedy local reranking strategies, for processing several recommendations at a time. These rerankers, given a set of recommendations, sequentially process them one by one. Those recommendations which are processed later are aware of the previously processed recommendations.

  • Field Summary

    Fields 
    Modifier and Type Field Description
    protected int cutOff
    Maximum length of the rankings

  • Constructor Summary

    Constructors 
    Constructor Description
    LocalGreedyReranker​(int cutOff)
    Constructor.
    LocalGreedyReranker​(int cutOff, int seed)
    Constructor

  • Method Summary

    Modifier and Type Method Description
    protected static int[] getBasePerm​(int n)
    Gets the base permutation (the i-th element remains at the i-th position)
    private es.uam.eps.ir.ranksys.core.Recommendation<U,​I> permuteRecommendation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int[] perm)
    Given a recommendation and a permutation, builds a new recommendation with the changed order.
    protected int[] rerankPermutation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int maxLength)
    Given a recommendation, permutates it according to the given criteria
    protected es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rerankRecommendation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int maxLength)
    Given a recommendation, reranks it.
    protected int selectItem​(U u, it.unimi.dsi.fastutil.ints.IntSortedSet remainingI, java.util.List<org.ranksys.core.util.tuples.Tuple2od<I>> list)
    Selects the next item to add in the permutation
    protected abstract void update​(U user, org.ranksys.core.util.tuples.Tuple2od<I> bestItemValue)
    Given a user, and the next value to add, updates the reranker parameters.
    protected abstract double value​(org.ranksys.core.util.tuples.Tuple2od<I> get)
    Computes the value for an item

    Methods inherited from class es.uam.eps.ir.relison.links.recommendation.reranking.global.local.LocalReranker

    rerankRecommendations, update

    Methods inherited from class java.lang.Object

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

  • Field Details

    • cutOff

      protected final int cutOff
      Maximum length of the rankings

  • Constructor Details

    • LocalGreedyReranker

      public LocalGreedyReranker​(int cutOff)
      Constructor.
      Parameters:
      cutOff - the maximum length of the definitive rankings

    • LocalGreedyReranker

      public LocalGreedyReranker​(int cutOff, int seed)
      Constructor
      Parameters:
      cutOff - the maximum length of the definitive rankings
      seed - random seed.

  • Method Details

    • rerankRecommendation

      protected es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rerankRecommendation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int maxLength)
      Description copied from class: LocalReranker
      Given a recommendation, reranks it.
      Specified by:
      rerankRecommendation in class LocalReranker<U,​I>
      Parameters:
      rec - the recommendation to rerank.
      maxLength - number of items to take from the original recommendation.
      Returns:
      the updated recommendation.

    • rerankPermutation

      protected int[] rerankPermutation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int maxLength)
      Given a recommendation, permutates it according to the given criteria
      Parameters:
      rec - original recommendation
      maxLength - the maximum length of the definitive rankings
      Returns:
      the permutation

    • permuteRecommendation

      private es.uam.eps.ir.ranksys.core.Recommendation<U,​I> permuteRecommendation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int[] perm)
      Given a recommendation and a permutation, builds a new recommendation with the changed order.
      Parameters:
      rec - the original recommendation.
      perm - the permutation.
      Returns:
      the permuted recommendation.

    • getBasePerm

      protected static int[] getBasePerm​(int n)
      Gets the base permutation (the i-th element remains at the i-th position)
      Parameters:
      n - the size of the base permutation
      Returns:
      the permutation.

    • selectItem

      protected int selectItem​(U u, it.unimi.dsi.fastutil.ints.IntSortedSet remainingI, java.util.List<org.ranksys.core.util.tuples.Tuple2od<I>> list)
      Selects the next item to add in the permutation
      Parameters:
      u - the user.
      remainingI - remaining items for user u
      list - the list of scored items.
      Returns:
      the next item.

    • update

      protected abstract void update​(U user, org.ranksys.core.util.tuples.Tuple2od<I> bestItemValue)
      Given a user, and the next value to add, updates the reranker parameters.
      Parameters:
      user - The user
      bestItemValue - The next value to add at the ranking

    • value

      protected abstract double value​(org.ranksys.core.util.tuples.Tuple2od<I> get)
      Computes the value for an item
      Parameters:
      get - The item, along its original value.
      Returns:
      the value.