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From yypvsxf19870706 <yypvsxf19870...@gmail.com>
Subject Re: 答复: Why hadoop is spawing two map over file size 1.5 KB ?
Date Sat, 16 Mar 2013 05:03:40 GMT

We just have discussed about the similar problem(the title is Increase the number of mappers
in PM mode),as I thought.

First of all you can not setup the the number of mappers.however you change the mapred.max.split.size,
or mapred.min.split.size ,the number of the mapper will change automatically.

I think the two mappers which you got in your situation,that is because the value of the mapred.max.split.size,
or mapred.min.split.size.
Do please check that .and appreciate that you give the results.


发自我的 iPhone

在 2013-3-15,0:04,王志强 <wangzhiqiang@360.cn> 写道:

> please check parameter "mapred.map.tasks" is equals to 2?
> 发件人: Yanbo Liang [yanbohappy@gmail.com]
> 发送时间: 2013年3月14日 23:11
> 收件人: user@hadoop.apache.org
> 主题: Re: Why hadoop is spawing two map over file size 1.5 KB ?
> I guess may be one of them is the speculative execution.
> You can check the parameter "mapred.map.tasks.speculative.execution" to ensure whether
it is allowed speculative execution. 
> You can get the precise information that whether it is speculative map task from the
tasktracker log.
> 2013/3/12 samir das mohapatra <samir.helpdoc@gmail.com>
>> Hi All,
>>   I have very fundamental doubt, I have file having size 1.5KB and block size is
default block size, But i could see two mapper it got creted during the Job. Could you please
help  to get whole picture why it is .
>> Regards,
>> samir.

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