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From maha <m...@umail.ucsb.edu>
Subject Re: Flow of control
Date Fri, 31 Dec 2010 04:58:52 GMT
Very helpful :) thanks Ping.

Maha

On Dec 30, 2010, at 6:13 PM, li ping wrote:

> On Fri, Dec 31, 2010 at 9:28 AM, maha <maha@umail.ucsb.edu> wrote:
> 
>> Hi,
>> 
>> (1) I declared a global variable in my hadoop mainClass which gets
>> initialized in the 'run' function of this mainClass. When I try to access
>> this global static variable from the MapperClass, it appears to be
>> uninitialized.
>> 
>>       Why is that? Is it because of the parallel execution of Hadoop
>> functions ? but , isn't the 'run' function supposed to be the one to run
>> first and prepare all the job configurations before the Maps even start?
>> 
> The Mapper will run on a remote machine, in other JVM, so the variable you
> set in Main class can not be shared with other VM.
> 
>> 
>> (2) Fig 4.5 in http://developer.yahoo.com/hadoop/tutorial/module4.html shows the
inputFormat to be the one running before the maps. My question is
>> in which node? The JobTracker node?
>> I think it should run on JobTracker, The inputFormat will split the file
>> and the map function will read the every splited file.
>> Thank you,
>>      Maha
> 
> 
> 
> 
> -- 
> -----李平


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