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https://issues.apache.org/jira/browse/LUCENE-7132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15210008#comment-15210008
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Ahmet Arslan commented on LUCENE-7132:
--------------------------------------
It is really hard to decipher what is going on inside the good old
TFIDFSimilarity.
{code:title=TFIDFSimilarity.IDFStats.normalize|borderStyle=solid}
@Override
public void normalize(float queryNorm, float boost) {
this.boost = boost;
this.queryNorm = queryNorm;
queryWeight = queryNorm * boost * idf.getValue();
value = queryWeight * idf.getValue(); // idf for document
}
{code}
* Why query weight has a IDF multiplicand?
* Why TFIDFSimilarity.IDFStats#value is set to IDF square?
* Why TFIDFSimilarity.IDFStats#value is need even though we have
TFIDFSimilarity.IDFStats.idf.getValue();
* TFIDFSimilarity.TFIDFSimScorer#score returns tf(freq) * IDFStats.value which
looks tfxIDFxIDF to me.
> ScoreDoc.score() returns a different value than that of Explanation's
> ---------------------------------------------------------------------
>
> Key: LUCENE-7132
> URL: https://issues.apache.org/jira/browse/LUCENE-7132
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/search
> Affects Versions: 5.5
> Reporter: Ahmet Arslan
> Assignee: Steve Rowe
> Attachments: LUCENE-7132.patch, SOLR-8884.patch, SOLR-8884.patch,
> debug.xml
>
>
> Some of the folks
> [reported|http://find.searchhub.org/document/80666f5c3b86ddda] that sometimes
> explain's score can be different than the score requested by fields
> parameter. Interestingly, Explain's scores would create a different ranking
> than the original result list. This is something users experience, but it
> cannot be re-produced deterministically.
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