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From "Yonik Seeley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2936) score and explain don't match
Date Wed, 23 Feb 2011 14:28:38 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12998383#comment-12998383
] 

Yonik Seeley commented on LUCENE-2936:
--------------------------------------

I'm not sure why this is a quantization issue... SmallFloat handles underflow by mapping to
the smallest number greater than 0, so the only way to get a 0 field norm is an explicit boost
of 0.

Anyway, if we want to discard explicit representation for 0, some of the code that handled
these edge cases should also be modified:
{code}
    if (smallfloat < fzero) {
      return (bits<=0) ?
        (byte)0   // negative numbers and zero both map to 0 byte
       :(byte)1;  // underflow is mapped to smallest non-zero number.
{code}

> score and explain don't match
> -----------------------------
>
>                 Key: LUCENE-2936
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2936
>             Project: Lucene - Java
>          Issue Type: Bug
>    Affects Versions: 2.9.4, 3.0.3, 3.1, 4.0
>            Reporter: Koji Sekiguchi
>            Assignee: Robert Muir
>            Priority: Minor
>         Attachments: LUCENE-2936.patch, LUCENE-2936.patch, TestScore.java
>
>
> I've faced this problem recently. I'll attach a program to reproduce the problem soon.
The program outputs the following:
> {noformat}
> ** score = 0.10003257
> ** explain
> 0.050016284 = (MATCH) product of:
>   0.15004885 = (MATCH) sum of:
>     0.15004885 = weight(f1:"note book" in 0), product of:
>       0.3911943 = queryWeight(f1:"note book"), product of:
>         0.61370564 = idf(f1: note=1 book=1)
>         0.6374299 = queryNorm
>       0.38356602 = fieldWeight(f1:"note book" in 0), product of:
>         1.0 = tf(phraseFreq=1.0)
>         0.61370564 = idf(f1: note=1 book=1)
>         0.625 = fieldNorm(field=f1, doc=0)
>   0.33333334 = coord(1/3)
> {noformat}

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