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From Chris Hostetter <hossman_luc...@fucit.org>
Subject Re: queryNorm affect on score
Date Sat, 28 Feb 2009 17:35:55 GMT

: I guess I don't really understand this comment in the similarity java doc
: then:
: 
: http://lucene.apache.org/java/2_4_0/api/org/apache/lucene/search/Similarity.html#formula_queryNorm
: 
: *queryNorm(q) * is a normalizing factor used to make scores between queries
: comparable.

that comment should probably be removed ... in situations where you 
deal with simple query types, and matching query structures, the queryNorm 
*can* be used to make scores semi-comparable.

To be 100% correct about what the queryNorm does in all cases: it 
normalizes each of the constituent values that are used in the score 
computation relative to the other constituent values.  the main value I've 
seen from it is that it prevents a loss of floating point accuracy that 
can result from addition/multiplication of large values.



-Hoss


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