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From: "Oliver Xu" <oliver.xuyong@gmail.com>
To: <java-user@lucene.apache.org>
Subject: A Problem in Customizing DefaultSimilarity
Date: Wed, 12 Jun 2013 21:00:01 +0800
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Dear,

=20

I built my own scoring class by extending the DefaultSimilarity. Three =
major
methods from DefaultSimilarity were overrided, including:

1. public float lengthNorm(FieldInvertState state)

2. public float tf(float freq)

3.public float idf(long docFreq, long numDocs)

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However, with embedded printing sentences (they are used to indicate =
which
and when a method is called by printing messages to console), I found =
only
tf() and idf() were called during a search process. The method =
lengthNorm(),
which is really what I wanted to work on, was never called.

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I rolled back to Lucene350 and checked again. The DefaultSimilarity =
under
Lucene 350 uses a computeNorm() method instead of lengthNorm(). And =
again,
the overrided computeNorm() is never called either.

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I used explanation() to check the components of each score for a =
document.
Besides the idf and tf scores, I did find a fieldNorm score, which has
something to do with the document length.

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My questions are:

1.       Why are the overrided lengthNorm() (under Lucene410) or
computeNorm() (under Lucene350) methods not called during a searching
process?

2.       How and where is fieldNorm calculated?

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Thank you very much!

=20

Oliver

=20

Oliver Xu(=D0=EC=D3=C0)
Aigine InfoTech Co.=A3=A8=D3=EF=C7=E6=BF=C6=BC=BC=A3=A9
W: <http://www.aigine.com> www.aigine.com
T: +86-189189 02886
E:  <mailto:oliver.xu@aigine.com> oliver.xu@aigine.com
MSN: oliver_xuyong@msn.com
Weibo: =D3=EF=C7=E6-=BC=AF=CC=E5=D6=C7=BB=DB=B1=E0=B3=CC

=20


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