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Posted to common-dev@hadoop.apache.org by "Christian Kunz (JIRA)" <ji...@apache.org> on 2008/09/23 01:17:44 UTC

[jira] Commented: (HADOOP-2771) changing the number of reduces dramatically changes the time of the map time

    [ https://issues.apache.org/jira/browse/HADOOP-2771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12633556#action_12633556 ] 

Christian Kunz commented on HADOOP-2771:
----------------------------------------

Sorry for the late response.
No, this job does not have a combiner. And the job execution times of the map tasks do not have large variations.

> changing the number of reduces dramatically changes the time of the map time
> ----------------------------------------------------------------------------
>
>                 Key: HADOOP-2771
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2771
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.17.1
>            Reporter: Owen O'Malley
>             Fix For: 0.20.0
>
>
> By changing the number of reduces, the time for an individual map changes radically. By running the same program and data with different numbers of reduces (2500, 7500, 25000) the times for each map changed radically (0:50, 1:20, 5h).

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