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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (HADOOP-3442) QuickSort may get into unbounded recursion
Date Tue, 10 Jun 2008 17:55:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12603949#action_12603949
] 

szetszwo edited comment on HADOOP-3442 at 6/10/08 10:53 AM:
--------------------------------------------------------------------------

> Even with all these fixes, I still believe it is good to add randomization to pivotal
selection (or randomize the input data upfront).

I also like randomized quick sort.  However, we better fix the stack overflow problem first.
 Then, we could think about how to improve the sorting algorithm.

> The 2*log\(n)  heuristic was intended to bail out of a worst case, not to protect against
the StackOverflowError

I think the 2*log n heuristic not only bail out of worst cases but also good cases since it
is overly strict.

I agree that we should force on fixing the problem in this issue.  3442-3.patch is already
very good.  +1


      was (Author: szetszwo):
    > Even with all these fixes, I still believe it is good to add randomization to pivotal
selection (or randomize the input data upfront).

I also like randomized quick sort.  However, we better fix the stack overflow problem first.
 Then, we could think about how to improve the sorting algorithm.

> The 2*log(n) heuristic was intended to bail out of a worst case, not to protect against
the StackOverflowError

I think the 2*log(n) heuristic not only bail out of worst cases but also good cases since
it is overly strict.

I agree that we should force on fixing the problem in this issue.  3442-3.patch is already
very good.  +1

  
> QuickSort may get into unbounded recursion
> ------------------------------------------
>
>                 Key: HADOOP-3442
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3442
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.17.0
>            Reporter: Runping Qi
>            Assignee: Chris Douglas
>            Priority: Blocker
>             Fix For: 0.17.1, 0.18.0
>
>         Attachments: 3442-0.patch, 3442-0v17.patch, 3442-1.patch, 3442-2.patch, 3442-3.patch,
CheckSortBuffer.java, HADOOP-3442.patch, overflow.zip, spillbuffers.patch
>
>


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