Thanks a lot....it is truly cause by the length normalization there. I follow
your suggestion and change it to 1.0f. Now it works properly.
Thanks again
Ahmet Arslan wrote:
>
>
>> yah, before this i used default lucene...but i dont know
>> what end up wrong...some results with only single word matching when to
>> the top of the results.
>
> Hmm. Interesting. It seems that length normalization causing this. Very
> short documents with only single word matching getting high score due to
> length normalization. The documents containing all of the query terms are
> probably very long and getting lower score. Lucene punishes long
> documents, and favors short documents.
>
> Can you verify/confirm my guess looking at the document lengths of the
> result set? Also org.apache.lucene.search.Explanation describes the score
> computation for document and query.
>
> There is an excellent publication [1] [2] (in section 4.1 and 4.2) about
> lucene score modification. SweetSpotSimilarity [3] with the appropriate
> parameters (steepness, min, and max) can solve your problem.
>
> Alternatively if your requirement is very important (you don't care about
> long documents taking over) then you can try to extend the
> DefaultSimilarity so that it will ignore the document length. Just return
> 1.
>
> public float lengthNorm(String fieldName, int numTerms) {
> return 1.0f;
> }
>
>
>> This i assumed is due to the score of the result being to
>> high. Tat's why i am trying to add additional boost
>
> I don't think there exists such a boosting mechanism.
>
> Ahmet
>
> [1]
> http://wiki.apache.org/lucene-java/TREC_2007_Million_Queries_Track_-_IBM_Haifa_Team
> [2]http://trec.nist.gov/pubs/trec16/papers/ibm-haifa.mq.final.pdf
> [3]http://lucene.apache.org/java/2_4_1/api/org/apache/lucene/misc/SweetSpotSimilarity.html
>
>
>
>
>
>
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