lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Yonik Seeley (JIRA)" <>
Subject [jira] Commented: (LUCENE-954) Toggle score normalization in Hits
Date Sun, 17 Feb 2008 13:38:34 GMT


Yonik Seeley commented on LUCENE-954:

Normalization is only applied to the queryWeight part of the score (the part the same for
all documents), but not to the fieldWeight.  idf and norms can both be > 1.

> Toggle score normalization in Hits
> ----------------------------------
>                 Key: LUCENE-954
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>    Affects Versions: 2.2
>         Environment: any
>            Reporter: Christian Kohlschütter
>         Attachments: hits-scoreNorm.patch
> The current implementation of the "Hits" class sometimes performs score normalization.
> In particular, whenever the top-ranked score is bigger than 1.0, it is normalized to
a maximum of 1.0.
> In this case, Hits may return different score results than TopDocs-based methods.
> In my scenario (a federated search system), Hits delievered just plain wrong results.
> I was merging results from several sources, all having homogeneous statistics (similar
to MultiSearcher, but over the Internet using HTTP/XML-based protocols).
> Sometimes, some of the sources had a top-score greater than 1, so I ended up with garbled
> I suggest to add a switch to enable/disable this score-normalization at runtime.
> My patch (attached) has an additional peformance benefit, since score normalization now
occurs only when Hits#score() is called, not when creating the Hits result list. Whenever
scores are not required, you save one multiplication per retrieved hit (i.e., at least 100
multiplications with the current implementation of Hits).

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

To unsubscribe, e-mail:
For additional commands, e-mail:

View raw message