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From Erik Hatcher <e...@ehatchersolutions.com>
Subject Re: Lucene scoring bounds ??
Date Mon, 20 Jun 2005 12:49:20 GMT

On Jun 18, 2005, at 7:39 PM, Paul Libbrecht wrote:
> I read the lucene-book about scoring and read a bit of the javadoc  
> but I can't seem to find somewhere expectations of the bouds for  
> the score value.
> I had believe the score would end up between 0 and 1 but I seem to  
> keep having values under 0.2. It may be due to my special requests  
> but... how can I be sure of this ?

Hits from all non-HitCollector searches are "normalized".  Normalized  
in this sense means that if the top-scoring document scores higher  
than 1.0 it is normalized to 1.0 and that ratio is used to normalize  
all scores.  However, if the top-scoring document is under 1.0, the  
scores are left as-is.

Searches using a HitCollector are always left as-is.

Have a look at IndexSearcher.explain() results for document/query  
combinations to see what is causing the lower than expected scores.

     Erik


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