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From "David Smiley (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-2761) FSTLookup should use long-tail like discretization instead of proportional (linear)
Date Wed, 14 Sep 2011 20:53:08 GMT

    [ https://issues.apache.org/jira/browse/SOLR-2761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13104864#comment-13104864
] 

David Smiley commented on SOLR-2761:
------------------------------------

I recommend that we follow through with the alternative suggested in the source code comment:
sort by weight and divide evenly.  That will handle the actual distribution in the data no
matter what the curve looks like.

> FSTLookup should use long-tail like discretization instead of proportional (linear)
> -----------------------------------------------------------------------------------
>
>                 Key: SOLR-2761
>                 URL: https://issues.apache.org/jira/browse/SOLR-2761
>             Project: Solr
>          Issue Type: Improvement
>          Components: spellchecker
>    Affects Versions: 3.4
>            Reporter: David Smiley
>            Priority: Minor
>
> The Suggester's FSTLookup implementation discretizes the term frequencies into a configurable
number of buckets (configurable as "weightBuckets") in order to deal with FST limitations.
The mapping of a source frequency into a bucket is a proportional (i.e. linear) mapping from
the minimum and maximum value. I don't think this makes sense at all given the well-known
long-tail like distribution of term frequencies. As a result of this problem, I've found it
necessary to increase weightBuckets substantially, like >100, to get quality suggestions.


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