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Message-ID: <940568575.1252509898349.JavaMail.jira@brutus>
Date: Wed, 9 Sep 2009 08:24:58 -0700 (PDT)
From: "Tom White (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-956) Shuffle should be broken down to
 only two phases (copy/reduce) instead of three (copy/sort/reduce)
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12753123#action_12753123 ] 

Tom White commented on MAPREDUCE-956:
-------------------------------------

The sort phase is actually when the map-outputs are being merged prior to being fed to the reducer. Could you give a bit more detail about what has changed - presumably the merging still takes place, so perhaps "sort phase" should just be renamed to "merge phase". 

> Shuffle should be broken down to only two phases (copy/reduce) instead of three (copy/sort/reduce)
> --------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-956
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-956
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: task
>    Affects Versions: 0.21.0
>            Reporter: Jothi Padmanabhan
>
> For the progress calculations and displaying on the UI, shuffle, in its current form,  is decomposed into three phases (copy/sort/reduce). Actually, the sort phase is no longer applicable. I think we should just reduce the number of phases to two and assign 50% weight-age to each of copy and reduce phases. Thoughts?

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