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Re: reducer tasks start time issue
Hi Lin,

Reduce task starts as soon as output is ready from Mappers. The reduce
method does not get called until all Mappers are done. If that's not the
case, all operations which are not commutative and associative will yield
incorrect result.

Thanks and Regards,

Rishi Yadav

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On Sat, Dec 22, 2012 at 5:25 AM, Lin Ma <[EMAIL PROTECTED]> wrote:

> Hi guys,
>
> Supposing in a Hadoop job, there are both mappers and reducers. My
> question is, reducer tasks cannot begin until all mapper tasks complete? If
> so, why designed in this way?
>
> thanks in advance,
> Lin
>
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Lin Ma 2012-12-23, 15:09
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Harsh J 2012-12-22, 16:15
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Lin Ma 2012-12-23, 15:09