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Posted to mapreduce-user@hadoop.apache.org by Pedro Costa <ps...@gmail.com> on 2011/03/25 18:09:27 UTC

map tasks vs launched map tasks

Hi,

during the setup phase and the cleanup phase of the tasks, the Hadoop
MR uses map tasks to do it. These tasks appears in the counters shown
at the end of an example?
For example, the counter below shows that my example ran 9 map tasks
and 2 reduce tasks, but the Launched map task has the value 13. The 4
more tasks are the one used at setup and cleanup phase?

[code]
11/03/25 17:04:26 INFO mapred.JobClient:532     Launched reduce tasks=2
11/03/25 17:04:26 INFO mapred.JobClient:532     Total number map tasks=9
11/03/25 17:04:26 INFO mapred.JobClient:532     Launched map tasks=13
11/03/25 17:04:26 INFO mapred.JobClient:532     Data-local map tasks=9
[/code]

-- 
Pedro

Re: map tasks vs launched map tasks

Posted by Allen Wittenauer <aw...@apache.org>.

On Mar 25, 2011, at 10:09 AM, Pedro Costa wrote:

> Hi,
> 
> during the setup phase and the cleanup phase of the tasks, the Hadoop
> MR uses map tasks to do it. These tasks appears in the counters shown
> at the end of an example?
> For example, the counter below shows that my example ran 9 map tasks
> and 2 reduce tasks, but the Launched map task has the value 13. The 4
> more tasks are the one used at setup and cleanup phase?

	Probably speculative execution