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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 15:59:29 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007524#comment-13007524
] 

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

Ok, i feel better now.

I think i have an explanation why the test doesn't "hang".
I think its because the automata we generate are pretty damn small (might are significantly
larger).
I think for our testing this is just fine, and actually desirable, as it helps debugging.

The only largeish automata lucene tests through this stuff are for levenshtein, and we supply
'true' 
here (since we know its finite) and avoid this method entirely... and even those are "special"
in that
they always have the same general "shape"


> 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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