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MapReduce >> mail # user >> number of reducers


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jamal sasha 2012-11-20, 19:38
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Bejoy KS 2012-11-20, 20:09
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RE: number of reducers
I specify mine inside mapred-site.xml

<property>
    <name>mapred.reduce.tasks</name>
    <value>20</value>
  </property>

Rgds,
AK47
From: Bejoy KS [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, November 20, 2012 3:10 PM
To: [EMAIL PROTECTED]
Subject: Re: number of reducers

Hi Sasha

By default the number or reducers are set to be 1. If you want more you need to specify it as

hadoop jar myJar.jar myClass -D mapred.reduce.tasks=20 ...
Regards
Bejoy KS

Sent from handheld, please excuse typos.
________________________________
From: jamal sasha <[EMAIL PROTECTED]>
Date: Tue, 20 Nov 2012 14:38:54 -0500
To: <[EMAIL PROTECTED]>
ReplyTo: [EMAIL PROTECTED]
Subject: number of reducers

Hi,

  I wrote a simple map reduce job in hadoop streaming.

I am wondering if I am doing something wrong ..

While number of mappers are projected to be around 1700.. reducers.. just 1?

It's couple of TB's worth of data.

What can I do to address this.

Basically mapper looks like this

For line in sys.stdin:

    Print line

Reducer

For line in sys.stdin:

    New_line = process_line(line)

    Print new_line

Thanks

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alxsss@... 2012-11-20, 22:00
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jamal sasha 2012-11-20, 20:24
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Harsh J 2012-11-21, 04:08