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Date: Tue, 11 Sep 2012 17:00:57 +0530
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Subject: Re: what's the default reducer number?
From: Bejoy Ks <bejoy.hadoop@gmail.com>
To: user@hadoop.apache.org
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Hi Lin

The default value for number of reducers is 1

<name>mapred.reduce.tasks</name>
  <value>1</value>

It is not determined by data volume. You need to specify the number of
reducers for your mapreduce jobs as per your data volume.

Regards
Bejoy KS

On Tue, Sep 11, 2012 at 4:53 PM, Jason Yang <lin.yang.jason@gmail.com>wrote:

> Hi, all
>
> I was wondering what's the default number of reducer if I don't set it in
> configuration?
>
> Will it change dynamically according to the output volume of Mapper?
>
> --
> YANG, Lin
>
>

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Hi Lin<div><br></div><div>The default value for number of reducers is 1</di=
v><div><br></div><div><div>&lt;name&gt;mapred.reduce.tasks&lt;/name&gt;</di=
v><div>=A0 &lt;value&gt;1&lt;/value&gt;</div><div><br></div><div>It is not =
determined by data volume. You need to specify the number of reducers for y=
our mapreduce jobs as per your data volume.</div>
<div><br></div><div>Regards</div><div>Bejoy KS</div><br><div class=3D"gmail=
_quote">On Tue, Sep 11, 2012 at 4:53 PM, Jason Yang <span dir=3D"ltr">&lt;<=
a href=3D"mailto:lin.yang.jason@gmail.com" target=3D"_blank">lin.yang.jason=
@gmail.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">Hi, all<div><br></div><div>I was wondering w=
hat&#39;s the default number of reducer if I don&#39;t set it in configurat=
ion?</div>
<div><br></div><div>Will it change dynamically according to the output volu=
me of Mapper?</div><span class=3D"HOEnZb"><font color=3D"#888888">

<div><div><br></div>-- <br><div>YANG, Lin</div><br>
</div>
</font></span></blockquote></div><br></div>

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