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https://issues.apache.org/jira/browse/HADOOP-2771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12619154#action_12619154
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chris.douglas edited comment on HADOOP-2771 at 8/1/08 3:49 PM:
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Does this job run with a combiner? That would also add time spent in each spill
in proportion to the number of reducers. Is there large variation in the map
execution time, or are most fairly close to the average time?
was (Author: chris.douglas):
Does this job run with a combiner? That would also add time spent in each
spill in proportion to the number of reducers.
> 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
>
> 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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