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Date: Mon, 11 Jun 2007 13:40:26 -0700 (PDT)
From: "Owen O'Malley (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-1440) JobClient should not sort
 input-splits
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    [ https://issues.apache.org/jira/browse/HADOOP-1440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12503609 ] 

Owen O'Malley commented on HADOOP-1440:
---------------------------------------

It is just an easier explanation to users, if the first map returned from getSplits is map-0, the second is map-1, and so on. The problem from my point of view is just that right now the name of the task controls the scheduling of the task. They should be independent of each other.

> JobClient should not sort input-splits
> --------------------------------------
>
>                 Key: HADOOP-1440
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1440
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.12.3
>         Environment: All
>            Reporter: Milind Bhandarkar
>            Assignee: Milind Bhandarkar
>             Fix For: 0.14.0
>
>
> Currently, the JobClient sorts the InputSplits returned by InputFormat in descending order, so that the map tasks corresponding to larger input-splits are scheduled first for execution than smaller ones. However, this causes problems in applications that produce data-sets partitioned similarly to the input partition with -reducer NONE.
> With -reducer NONE, map task i produces part-i. Howver, in the typical applications that use -reducer NONE it should produce a partition that has the same index as the input parrtition.
> (Of course, this requires that each partition should be fed in its entirety to a map, rather than splitting it into blocks, but that is a separate issue.)
> Thus, sorting input splits should be either controllable via a configuration variable, or the FileInputFormat should sort the splits and JobClient should honor the order of splits.

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