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From "Dawid Weiss (JIRA)" <j...@apache.org>
Subject [jira] Assigned: (LUCENE-2933) Two-stage state expansion for the FST: distance-from-root and child-count criteria.
Date Mon, 21 Feb 2011 09:25:38 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-2933?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dawid Weiss reassigned LUCENE-2933:
-----------------------------------

    Assignee: Dawid Weiss

> Two-stage state expansion for the FST: distance-from-root and child-count criteria.
> -----------------------------------------------------------------------------------
>
>                 Key: LUCENE-2933
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2933
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Dawid Weiss
>            Assignee: Dawid Weiss
>            Priority: Trivial
>             Fix For: 4.0
>
>
> In the current implementation FST states are expanded into a binary search on labels
(from a vector of transitions) when the child count of a state exceeds a given predefined
threshold (NUM_ARCS_FIXED_ARRAY). This threshold affects automaton size and traversal speed
(as it turns out when benchmarked). For some degenerate (?) data sets, close-to-the-root nodes
could have a small number of children (below the threshold) and yet be traversed on every
single seek.
> A fix of this is to introduce two control thresholds: 
>   EXPAND state if (distance-from-root <= MIN_DISTANCE || children-count >= NUM_ARCS_FIXED_ARRAY)
> My plan is to create a data set that will prove this first and then to implement the
workaround above.

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