FAQ
Hi Jun,



Request you to go through this link:

http://wiki.apache.org/hadoop/HowManyMapsAndReduces



Following configuration may help you :

mapred.min.split.size

mapred.map.tasks (This is just a hint to InputFormat)



But how can I know how many mappers have been created while doing my job?

The implementation of InputFormat actually defines how many Mappers are
going to be in the submitted job.



Can I do some sets to make it only 2 mappers created and each mapper runs on
one node?

The scheduler implementation has the logic to schedule mappers and reducers.







Regards,
Subroto Sanyal

_____

From: 谭军
Sent: Sunday, August 07, 2011 12:15 PM
To: mapreduce-user@hadoop.apache.org
Subject: How can I know how many mappers created?



Hi,

I just want 2 mappers created to do my job for there are only 2 data nodes.

I think that is the most efficient.

But how can I know how many mappers have been created while doing my job?

Can I do some sets to make it only 2 mappers created and each mapper runs on
one node?

Thanks



--

Best regards!

Jun Tan

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