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From: Robert Muir <rcmuir@gmail.com>
Date: Wed, 17 Oct 2012 07:58:12 -0700
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 <CAOdYfZV9fTEJ2Hu-DPQ9vi_dvpsJo8UtRjPKJ5_RkApBP4mB+g@mail.gmail.com>
Subject: Re: Lucene 4.0 benchmark bug?
To: java-user@lucene.apache.org
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On Wed, Oct 17, 2012 at 6:48 AM, Zeynep P. <zpvie@yahoo.com> wrote:
>
> My index is created by lucene 3.6.

> Second problem, for the same collection MAP = 0.17 with default similarity,
> MAP= 0.07 with lucene 4.0 BM25 similarity (b=0.75, k1=1.2).

Did you read CHANGES.txt before doing this? This is really important to do.

Note: most of the models do rely upon index statistics that are new in
Lucene 4.0, so
for existing 3.x indexes its a good idea to upgrade your index to the
new format with IndexUpgrader first.

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