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Subject: RE: Normalized Scoring -- was RE: idf and explain(),
 was Re: Search and Scoring
Date: Thu, 21 Oct 2004 15:11:24 -0700
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Thread-Topic: Normalized Scoring -- was RE: idf and explain(),
 was Re: Search and Scoring
Thread-Index: AcS3tTGqHgvjHBfpQyyutMVZLZr4iwABE1Aw
From: "Chuck Williams" <chuck@manawiz.com>
To: "Lucene Developers List" <lucene-dev@jakarta.apache.org>

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The idf's are indeed computed locally, but I believe it is a simple bug =
in MultiSearcher.  The attached version of the test adds explain()'s to =
verify the problem is the idf's (and changes the Field construction to =
something that works in my 1.4.2 sources).

MultiSearcher.search() calls the separate searchers for each index.  =
That makes the IndexSearcher the current searcher when Similarity.idf() =
is reached.  Thus IndexSearcher.docFreq() is used instead of =
MultiSearcher.docFreq(), yielding the index-local idf's.

The best fix is not obvious to me, but it is just a code-structure =
issue.

Chuck

  > -----Original Message-----
  > From: Daniel Naber [mailto:daniel.naber@t-online.de]
  > Sent: Thursday, October 21, 2004 2:35 PM
  > To: Lucene Developers List
  > Subject: Re: Normalized Scoring -- was RE: idf and explain(), was =
Re:
  > Search and Scoring
  >=20
  > On Thursday 21 October 2004 23:03, Doug Cutting wrote:
  >=20
  > > Idf's are already computed globally across all indexes. =A0Tf's =
are
  > local
  > > to the document. =A0In short, scores from a MultiSearcher are the =
same
  > as
  > > when searching an IndexReader with the same documents.
  >=20
  > That doesn't seem to be the case in the attached test -- am I using
  > MultiSearcher in the wrong way or what might be the problem?
  > The output of the attached test is:
  >=20
  > 1+2 searched with Multisearcher:
  > two blah three score=3D0.70273256
  > one blah three score=3D0.35615897
  > one foo three score=3D0.35615897
  > one foobar three score=3D0.35615897
  >=20
  > 1+2 indexed together:
  > one blah three score=3D0.5911608
  > one foo three score=3D0.5911608
  > one foobar three score=3D0.5911608
  > two blah three score=3D0.5911608
  >=20
  > --
  > http://www.danielnaber.de


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