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From Felix Halim <felix.ha...@gmail.com>
Subject How to set the number of map tasks? (ver 0.20.2)
Date Mon, 21 Jun 2010 19:07:57 GMT
I'm using the new Job class:

http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/mapreduce/Job.html

There is a way to set the number of reduce tasks:

setNumReduceTasks(int tasks)

However, I don't see how to set the number of MAP tasks?

I tried to set it through mapred-site.xml :

	<property>
		<name>mapred.map.tasks</name>
		<value>500</value>
	</property>

It doesn't work either (launched map task is still small).

I'm wondering, do I have to rename the prefix from "mapred" to
"mapreduce"? like this (for all configurations?):

	<property>
		<name>mapreduce.map.tasks</name>
		<value>500</value>
	</property>

I added both, and it still doesn't work.

However, the old way of (using JobConf) works.

Is the new Job class is intended to not support altering the number of
map tasks?

FYI, setting the number of reduce tasks seemed to work using the new Job class.

Felix Halim

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