FAQ
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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  • Subroto Sanyal at Aug 8, 2011 at 4:33 am
    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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