Package org.apache.lucene.search.similarities

Class LMJelinekMercerSimilarity

java.lang.Object
org.apache.lucene.search.similarities.Similarity
org.apache.lucene.search.similarities.SimilarityBase
org.apache.lucene.search.similarities.LMSimilarity
org.apache.lucene.search.similarities.LMJelinekMercerSimilarity
public class LMJelinekMercerSimilarity extends LMSimilarity
Language model based on the Jelinek-Mercer smoothing method. From Chengxiang Zhai and John Lafferty. 2001. A study of smoothing methods for language models applied to Ad Hoc information retrieval. In Proceedings of the 24th annual international ACM SIGIR conference on Research and development in information retrieval (SIGIR '01). ACM, New York, NY, USA, 334-342.

The model has a single parameter, λ. According to said paper, the optimal value depends on both the collection and the query. The optimal value is around 0.1 for title queries and 0.7 for long queries.

  • Constructor Details

    • LMJelinekMercerSimilarity

      public LMJelinekMercerSimilarity(LMSimilarity.CollectionModel collectionModel, float lambda)
      Instantiates with the specified collectionModel and λ parameter.

    • LMJelinekMercerSimilarity

      public LMJelinekMercerSimilarity(float lambda)
      Instantiates with the specified λ parameter.

  • Method Details

    • getLambda

      public float getLambda()
      Returns the λ parameter.

    • getName

      public String getName()
      Description copied from class: LMSimilarity
      Returns the name of the LM method. The values of the parameters should be included as well.

      Used in LMSimilarity.toString()

      .
      Specified by:
      getName in class LMSimilarity