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From li ping <li.j...@gmail.com>
Subject Re: Flow of control
Date Fri, 31 Dec 2010 02:13:17 GMT
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


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