org.apache.solr.search.similarities
Class SweetSpotSimilarityFactory

java.lang.Object
  org.apache.solr.schema.SimilarityFactory
      org.apache.solr.search.similarities.DefaultSimilarityFactory
          org.apache.solr.search.similarities.SweetSpotSimilarityFactory

public class SweetSpotSimilarityFactory
extends DefaultSimilarityFactory

Factory for SweetSpotSimilarity.

SweetSpotSimilarity is an extension of DefaultSimilarity that provides additional tuning options for specifying the "sweetspot" of optimal tf and lengthNorm values in the source data.

In addition to the discountOverlaps init param supported by DefaultSimilarityFactory The following sets of init params are supported by this factory:

• Length Norm Settings:
  • lengthNormMin (int)
  • lengthNormMax (int)
  • lengthNormSteepness (float)
• Baseline TF Settings:
  • baselineTfBase (float)
  • baselineTfMin (float)
• Hyperbolic TF Settings:
  • hyperbolicTfMin (float)
  • hyperbolicTfMax (float)
  • hyperbolicTfBase (double)
  • hyperbolicTfOffset (float)

Note:

• If any individual settings from one of the above mentioned sets are specified, then all settings from that set must be specified.
• If Baseline TF settings are spcified, then Hyperbolic TF settings are not permitted, and vice versa. (The settings specified will determine wether SweetSpotSimilarity.baselineTf(float) or SweetSpotSimilarity.hyperbolicTf(float) will be used.

Example usage...

 <!-- using baseline TF -->
 <fieldType name="text_baseline" class="solr.TextField"
            indexed="true" stored="false">
   <analyzer class="org.apache.lucene.analysis.standard.StandardAnalyzer"/>
   <similarity class="solr.SweetSpotSimilarityFactory">
     <!-- TF -->
     <float name="baselineTfMin">6.0</float>
     <float name="baselineTfBase">1.5</float>
     <!-- plateau norm -->
     <int name="lengthNormMin">3</int>
     <int name="lengthNormMax">5</int>
     <float name="lengthNormSteepness">0.5</float>
   </similarity>
 </fieldType>
 
 <!-- using hyperbolic TF -->
 <fieldType name="text_hyperbolic" class="solr.TextField"
            indexed="true" stored="false" >
   <analyzer class="org.apache.lucene.analysis.standard.StandardAnalyzer"/>
   <similarity class="solr.SweetSpotSimilarityFactory">
     <float name="hyperbolicTfMin">3.3</float>
     <float name="hyperbolicTfMax">7.7</float>
     <double name="hyperbolicTfBase">2.718281828459045</double> <!-- e -->
     <float name="hyperbolicTfOffset">5.0</float>
     <!-- plateau norm, shallower slope -->
     <int name="lengthNormMin">1</int>
     <int name="lengthNormMax">5</int>
     <float name="lengthNormSteepness">0.2</float>
   </similarity>
 </fieldType>
 

See Also:

The javadocs for the individual methods in SweetSpotSimilarity for SVG diagrams showing how the each function behaves with various settings/inputs.

Field Summary

Fields inherited from class org.apache.solr.search.similarities.DefaultSimilarityFactory

DISCOUNT_OVERLAPS, discountOverlaps

Fields inherited from class org.apache.solr.schema.SimilarityFactory

CLASS_NAME, params

Constructor Summary

SweetSpotSimilarityFactory()

Method Summary

Similarity	getSimilarity()
void	init(SolrParams params)

Methods inherited from class org.apache.solr.schema.SimilarityFactory

getClassArg, getNamedPropertyValues, getParams

Methods inherited from class java.lang.Object

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

Constructor Detail

SweetSpotSimilarityFactory

public SweetSpotSimilarityFactory()

Method Detail

init

public void init(SolrParams params)

Overrides:

init in class DefaultSimilarityFactory

getSimilarity

public Similarity getSimilarity()

Overrides:

getSimilarity in class DefaultSimilarityFactory