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.
在 2013-3-15，0:04，王志强 <[EMAIL PROTECTED]> 写道：
> please check parameter "mapred.map.tasks" is equals to 2?
> 发件人: Yanbo Liang [[EMAIL PROTECTED]]
> 发送时间: 2013年3月14日 23:11
> 收件人: [EMAIL PROTECTED]
> 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 <[EMAIL PROTECTED]>
>> 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 .