Hi, On Tue, Aug 28, 2012 at 8:32 AM, Abhishek <abhishek.dod...@gmail.com> wrote: > Hi all, > > I just want to know that, based on what factor map reduce framework decides > number of reducers to launch for a job
The framework does not auto-determine the number of reducers for a job. That is purely user-or-client-program-supplied presently. > By default only one reducer will be launched for a given job is this right? > If we explicitly does not mention number to launch via command line or driver > class. Yes, by default the number of reduce tasks is configured to be one. > If i choose to decide number of reducers to mention explicitly, what should I > consider.Because choosing in appropriate number of reducer hampers the > performance. See http://wiki.apache.org/hadoop/HowManyMapsAndReduces -- Harsh J
