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

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 <[EMAIL PROTECTED]>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
>
>

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 <[EMAIL PROTECTED]>

> 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 <[EMAIL PROTECTED]>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

Hi Lin

The default values for all the properties are in
core-default.xml
hdfs-default.xml and
mapred-default.xml
Regards
Bejoy KS
On Tue, Sep 11, 2012 at 5:06 PM, Jason Yang <[EMAIL PROTECTED]>wrote:

> 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 <[EMAIL PROTECTED]>
>
>> 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 <[EMAIL PROTECTED]>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
>
>

Just to add the name is depreciated in new Hadoop
Try to find
mapreduce.job.reduces

On Tue, Sep 11, 2012 at 9:43 PM, Bejoy Ks <[EMAIL PROTECTED]> wrote:

> Hi Lin
>
> The default values for all the properties are in
> core-default.xml
> hdfs-default.xml and
> mapred-default.xml
>
>
> Regards
> Bejoy KS
>
>
> On Tue, Sep 11, 2012 at 5:06 PM, Jason Yang <[EMAIL PROTECTED]>wrote:
>
>> 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 <[EMAIL PROTECTED]>
>>
>>> 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 <[EMAIL PROTECTED]>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
>>
>>
>

All right, I got it.

Thank you very much~

2012/9/11 Jagat Singh <[EMAIL PROTECTED]>

> Just to add the name is depreciated in new Hadoop
> Try to find
> mapreduce.job.reduces
>
>
>
>
> On Tue, Sep 11, 2012 at 9:43 PM, Bejoy Ks <[EMAIL PROTECTED]> wrote:
>
>> Hi Lin
>>
>> The default values for all the properties are in
>> core-default.xml
>> hdfs-default.xml and
>> mapred-default.xml
>>
>>
>> Regards
>> Bejoy KS
>>
>>
>> On Tue, Sep 11, 2012 at 5:06 PM, Jason Yang <[EMAIL PROTECTED]>wrote:
>>
>>> 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 <[EMAIL PROTECTED]>
>>>
>>>> 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 <[EMAIL PROTECTED]>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
>>>
>>>
>>
>
--
YANG, Lin