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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2970) SpecialOperations.isFinite can have TERRIBLE TERRIBLE runtime in certain situations
Date Wed, 16 Mar 2011 16:10:31 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007531#comment-13007531
] 

Robert Muir commented on LUCENE-2970:
-------------------------------------

i ran the random test for a good hour:
{noformat}
junit-sequential:
    [junit] Testsuite: org.apache.lucene.util.automaton.TestSpecialOperations
    [junit] Tests run: 10000, Failures: 0, Errors: 0, Time elapsed: 3,908.995 sec
    [junit]
{noformat}

I'll rename the old method (in the testUtil for testing correctness) to *Slow as Mike suggested,
with an additional warning that if we ever start generating larger automata for testing, it
will
blow up, and commit.


> SpecialOperations.isFinite can have TERRIBLE TERRIBLE runtime in certain situations
> -----------------------------------------------------------------------------------
>
>                 Key: LUCENE-2970
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2970
>             Project: Lucene - Java
>          Issue Type: Bug
>    Affects Versions: 4.0
>            Reporter: Robert Muir
>            Assignee: Robert Muir
>             Fix For: 4.0
>
>         Attachments: LUCENE-2970.patch
>
>
> in an application of mine, i experienced some very slow query times with finite automata
(all the DFAs are acyclic)
> It turned out, the slowdown is some terrible runtime in SpecialOperations.isFinite <--
this is used to determine if the DFA is acyclic or not.
> (in this case I am talking about even up to minutes of cpu).

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