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From Nirmalya Sengupta <sengupta.nirma...@gmail.com>
Subject Finding the average temperature
Date Sat, 13 Feb 2016 18:03:37 GMT
Hello Flinksters,

This is perhaps too trivial for most here in this forum, but I want to have
my understanding clear.

I want to find the average of temperatures coming in as a stream. The tuple
as the following fields:

probeID,readingTimeStamp,radiationLevel,photoSensor,humidity,ambientTemperature

The 'readingTimeStamp' field provides the 'Event Time', and this provides
the basis of the timeWindow(10) that I employ.

I _keyBy_ the 'readingTimeStamp' and collect readings for next 10 seconds,
and then I compute the average of the 'ambientTemperature'. After every 10
seconds, I want to be able to find the average temperature *so far* (a
single value).

Because my application defaults to parellelism == 4 (my laptop is 4 core),
my understanding is that just by using a combination of an appropriate
RichXXXFunction() and saving State in the RuntimeContext, I may not get the
correct result. This is because, depending the way the Keys are
distributed, 4 _different_  averages will be produced. Is this
understanding right? If so, is using a *Broadcast variable*, the solution?

Please help me plug the gap in understanding, if any.

-- Nirmalya

-- 
Software Technologist
http://www.linkedin.com/in/nirmalyasengupta
"If you have built castles in the air, your work need not be lost. That is
where they should be.
Now put the foundation under them."

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