hadoop-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Rishi Yadav <ri...@infoobjects.com>
Subject Re: reducer tasks start time issue
Date Sat, 22 Dec 2012 16:09:46 GMT
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

(o) 408.988.2000x113 ||  (f) 408.716.2726

InfoObjects Inc || http://www.infoobjects.com *(Big Data Solutions)*

*INC 500 Fastest growing company in 2012 || 2011*

*Best Place to work in Bay Area 2012 - *SF Business Times and the Silicon
Valley / San Jose Business Journal

2041 Mission College Boulevard, #280 || Santa Clara, CA 95054

On Sat, Dec 22, 2012 at 5:25 AM, Lin Ma <linlma@gmail.com> 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

View raw message