forgot to add there is similar method for reducer as well job.setNumReduceTasks(0);
On Tue, Apr 30, 2013 at 3:56 PM, Nitin Pawar <nitinpawar...@gmail.com>wrote: > The *mapred*.*tasktracker*.*reduce*.*tasks*.*maximum* parameter sets the > maximum number of reduce tasks that may be run by an individual TaskTracker > server at one time. This is not per job configuration. > > he number of map tasks for a given job is driven by the number of input > splits and not by the mapred.map.tasks parameter. For each input split a > map task is spawned. So, over the lifetime of a mapreduce job the number of > map tasks is equal to the number of input splits. mapred.map.tasks is just > a hint to the InputFormat for the number of maps > > If you want to set max number of maps or reducers per job then you can set > the hints by using the job object you created > job.setNumMapTasks() > > Note this is just a hint and again the number will be decided by the input > split size. > > > On Tue, Apr 30, 2013 at 3:39 PM, Han JU <ju.han.fe...@gmail.com> wrote: > >> Thanks Nitin. >> >> What I need is to set slot only for a specific job, not for the whole >> cluster conf. >> But what I did does NOT work ... Have I done something wrong? >> >> >> 2013/4/30 Nitin Pawar <nitinpawar...@gmail.com> >> >>> The config you are setting is for job only >>> >>> But if you want to reduce the slota on tasktrackers then you will need >>> to edit tasktracker conf and restart tasktracker >>> On Apr 30, 2013 3:30 PM, "Han JU" <ju.han.fe...@gmail.com> wrote: >>> >>>> Hi, >>>> >>>> I want to change the cluster's capacity of reduce slots on a per job >>>> basis. Originally I have 8 reduce slots for a tasktracker. >>>> I did: >>>> >>>> conf.set("mapred.tasktracker.reduce.tasks.maximum", "4"); >>>> ... >>>> Job job = new Job(conf, ...) >>>> >>>> >>>> And in the web UI I can see that for this job, the max reduce tasks is >>>> exactly at 4, like I set. However hadoop still launches 8 reducer per >>>> datanode ... why is this? >>>> >>>> How could I achieve this? >>>> -- >>>> *JU Han* >>>> >>>> Software Engineer Intern @ KXEN Inc. >>>> UTC - Université de Technologie de Compiègne >>>> * **GI06 - Fouille de Données et Décisionnel* >>>> >>>> +33 0619608888 >>>> >>> >> >> >> -- >> *JU Han* >> >> Software Engineer Intern @ KXEN Inc. >> UTC - Université de Technologie de Compiègne >> * **GI06 - Fouille de Données et Décisionnel* >> >> +33 0619608888 >> > > > > -- > Nitin Pawar > -- Nitin Pawar