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From: Jason Yang <lin.yang.jason@gmail.com>
Date: Tue, 11 Sep 2012 19:36:28 +0800
Message-ID: 
 <CAE636z-1886i+-ynyOG4qOqV=sxMYvP0mAt_xma_zfVVUY6tpg@mail.gmail.com>
Subject: Re: what's the default reducer number?
To: user@hadoop.apache.org
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Hi, Bejoy

Thanks for you reply.

where could I find the default value of mapred.reduce.tasks ? I have
checked the core-site.xml, hdfs-site.xml and mapred-site.xml, but I haven't
found it.

2012/9/11 Bejoy Ks <bejoy.hadoop@gmail.com>

> 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
>>
>>
>


-- 
YANG, Lin

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Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

Hi, Bejoy<div><br></div><div>Thanks for you reply.</div><div><br></div><div=
>where could I find the default value of mapred.reduce.tasks ? I have check=
ed the core-site.xml, hdfs-site.xml and mapred-site.xml, but I haven&#39;t =
found it.<br>

<br><div class=3D"gmail_quote">2012/9/11 Bejoy Ks <span dir=3D"ltr">&lt;<a =
href=3D"mailto:bejoy.hadoop@gmail.com" target=3D"_blank">bejoy.hadoop@gmail=
.com</a>&gt;</span><br><blockquote class=3D"gmail_quote" style=3D"margin:0 =
0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">

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><span class=3D"HOEnZb"><font color=3D"#888=
888"><div>Bejoy KS</div></font></span><div><div class=3D"h5"><br><div class=
=3D"gmail_quote">On Tue, Sep 11, 2012 at 4:53 PM, Jason Yang <span dir=3D"l=
tr">&lt;<a href=3D"mailto:lin.yang.jason@gmail.com" target=3D"_blank">lin.y=
ang.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><font color=3D"#888888">

<div><div><br></div>-- <br><div>YANG, Lin</div><br>
</div>
</font></span></blockquote></div><br></div></div></div>
</blockquote></div><br><br clear=3D"all"><div><br></div>-- <br><div>YANG, L=
in</div><br>
</div>

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