LMDirichletSimilarity (The Adobe Experience Manager SDK 2022.11.9850.20221116T162329Z-220900)

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.LMDirichletSimilarity

```
public class LMDirichletSimilarity
extends LMSimilarity
```
Bayesian smoothing using Dirichlet priors. 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 formula as defined the paper assigns a negative score to documents that contain the term, but with fewer occurrences than predicted by the collection language model. The Lucene implementation returns 0 for such documents.

Nested Class Summary
- Nested classes/interfaces inherited from class org.apache.lucene.search.similarities.LMSimilarity
  LMSimilarity.CollectionModel, LMSimilarity.DefaultCollectionModel, LMSimilarity.LMStats
- Nested classes/interfaces inherited from class org.apache.lucene.search.similarities.Similarity
  Similarity.SimScorer, Similarity.SimWeight

Constructor Summary

Constructors
Constructor	Description
`LMDirichletSimilarity()`	Instantiates the similarity with the default μ value of 2000.
`LMDirichletSimilarity(float mu)`	Instantiates the similarity with the provided μ parameter.
`LMDirichletSimilarity(LMSimilarity.CollectionModel collectionModel)`	Instantiates the similarity with the default μ value of 2000.
`LMDirichletSimilarity(LMSimilarity.CollectionModel collectionModel, float mu)`	Instantiates the similarity with the provided μ parameter.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type Method Description

float getMu()
Returns the μ parameter.

java.lang.String getName()
Returns the name of the LM method.
- Methods inherited from class org.apache.lucene.search.similarities.LMSimilarity
  toString
- Methods inherited from class org.apache.lucene.search.similarities.SimilarityBase
  computeNorm, computeWeight, getDiscountOverlaps, log2, setDiscountOverlaps, simScorer
- Methods inherited from class org.apache.lucene.search.similarities.Similarity
  coord, queryNorm
- Methods inherited from class java.lang.Object
  equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - LMDirichletSimilarity
```
public LMDirichletSimilarity(LMSimilarity.CollectionModel collectionModel,
                             float mu)
```
    Instantiates the similarity with the provided μ parameter.
  - LMDirichletSimilarity
```
public LMDirichletSimilarity(float mu)
```
    Instantiates the similarity with the provided μ parameter.
  - LMDirichletSimilarity
```
public LMDirichletSimilarity(LMSimilarity.CollectionModel collectionModel)
```
    Instantiates the similarity with the default μ value of 2000.
  - LMDirichletSimilarity
```
public LMDirichletSimilarity()
```
    Instantiates the similarity with the default μ value of 2000.
- Method Detail
  - getMu
```
public float getMu()
```
    Returns the μ parameter.
  - getName
```
public java.lang.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