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

Class SwapGreedyReranker<U,​I>

java.lang.Object
es.uam.eps.ir.relison.links.recommendation.reranking.global.swap.SwapReranker<U,​I>
es.uam.eps.ir.relison.links.recommendation.reranking.global.swap.SwapGreedyReranker<U,​I>
Type Parameters:
U - type of the users.
I - type of the items.
All Implemented Interfaces:
GlobalReranker<U,​I>
Direct Known Subclasses:
SwapLambdaReranker
public abstract class SwapGreedyReranker<U,​I>
extends SwapReranker<U,​I>
Abstract greedy implementation of the swap reranking strategy for optimizing global properties of the system.

  • Field Summary

    Fields 
    Modifier and Type Field Description
    protected int cutOff
    The definitive size of the recommendation ranking (i.e.

    Fields inherited from class es.uam.eps.ir.relison.links.recommendation.reranking.global.swap.SwapReranker

    globalvalue

  • Constructor Summary

    Constructors 
    Constructor Description
    SwapGreedyReranker​(int cutOff)
    Constructor.

  • Method Summary

    Modifier and Type Method Description
    protected static int[] getBasePerm​(int n)
    Obtains the base permutation of size n.
    private es.uam.eps.ir.ranksys.core.Recommendation<U,​I> permuteRecommendation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int[] perm)
    Permutes a recommendation.
    protected int[] rerankPermutation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int maxLength)
    Obtains a permutation for a ranking that greedily optimizes the global metric.
    protected es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rerankRecommendation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int maxLength)
    Reranks the recommendation for a user.
    protected int selectItem​(U user, it.unimi.dsi.fastutil.ints.IntSortedSet remainingI, org.ranksys.core.util.tuples.Tuple2od<I> compared, java.util.List<org.ranksys.core.util.tuples.Tuple2od<I>> list)
    Select the next item to add.
    protected abstract void update​(U user, org.ranksys.core.util.tuples.Tuple2od<I> updated, org.ranksys.core.util.tuples.Tuple2od<I> old)
    Updates the value of the global metric.
    protected abstract double value​(org.ranksys.core.util.tuples.Tuple2od<I> get)
    Computes the value for a item.
    protected abstract double valuetop​(org.ranksys.core.util.tuples.Tuple2od<I> get)
    Computes the value for the top users.

    Methods inherited from class es.uam.eps.ir.relison.links.recommendation.reranking.global.swap.SwapReranker

    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
      The definitive size of the recommendation ranking (i.e. the number of user-item pairs we consider that we add to the system.

  • Constructor Details

    • SwapGreedyReranker

      public SwapGreedyReranker​(int cutOff)
      Constructor.
      Parameters:
      cutOff - the definitive size of the recommendation ranking.

  • 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: SwapReranker
      Reranks the recommendation for a user.
      Specified by:
      rerankRecommendation in class SwapReranker<U,​I>
      Parameters:
      rec - the original recommendation.
      maxLength - maximum length of the definitive ranking.
      Returns:
      the new recommendation.

    • rerankPermutation

      protected int[] rerankPermutation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int maxLength)
      Obtains a permutation for a ranking that greedily optimizes the global metric.
      Parameters:
      rec - the recommendation ranking.
      maxLength - the maximum number of items to consider.
      Returns:
      a permutation of the indexes.

    • permuteRecommendation

      private es.uam.eps.ir.ranksys.core.Recommendation<U,​I> permuteRecommendation​(es.uam.eps.ir.ranksys.core.Recommendation<U,​I> rec, int[] perm)
      Permutes a recommendation.
      Parameters:
      rec - the original recommendation.
      perm - the permutation of the data.
      Returns:
      the new recommendation.

    • getBasePerm

      protected static int[] getBasePerm​(int n)
      Obtains the base permutation of size n.
      Parameters:
      n - size of the permutation.
      Returns:
      an array containing the indexes.

    • selectItem

      protected int selectItem​(U user, it.unimi.dsi.fastutil.ints.IntSortedSet remainingI, org.ranksys.core.util.tuples.Tuple2od<I> compared, java.util.List<org.ranksys.core.util.tuples.Tuple2od<I>> list)
      Select the next item to add.
      Parameters:
      user - the target user of the recommendation.
      remainingI - elements outside the top k
      compared - the element we want to compare with the elements out of the top N.
      list - list of values for all the elements
      Returns:
      the selected item if we have to swap elements, -1 if not.

    • update

      protected abstract void update​(U user, org.ranksys.core.util.tuples.Tuple2od<I> updated, org.ranksys.core.util.tuples.Tuple2od<I> old)
      Updates the value of the global metric.
      Parameters:
      user - the user whose recommendation we are reranking.
      updated - the new item.
      old - the old item.

    • value

      protected abstract double value​(org.ranksys.core.util.tuples.Tuple2od<I> get)
      Computes the value for a item.
      Parameters:
      get - the item whose value we want to compute
      Returns:
      the value

    • valuetop

      protected abstract double valuetop​(org.ranksys.core.util.tuples.Tuple2od<I> get)
      Computes the value for the top users.
      Parameters:
      get - item between the top.
      Returns:
      the value for the top users.