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Date: Tue, 22 Apr 2008 13:46:13 +0300
From: Enis Soztutar <enis.soz.nutch@gmail.com>
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Hi,

The number of map tasks is supposed to be greater than the number of 
machines, so in your configuration, 6 map tasks is ok. However there 
should be another problem. Have you changed the code for word count?

Please ensure that the example code is unchanged and your configuration 
is right. Also you may want to try the latest stable release, which is 
0.16.3 at this point.

wangxiaowei wrote:
> hello, I am a Chinese user.I am using hadoop-0.15.3 now.The problem is that:I install hadoop with three nodes.One is taken as NameNode and JobTracker.The three are all taken as slaves. It dfs runs normally.I use your example of wordcount,the instruction is:bin/hadoop jar hadoop-0.15.3-examples.jar wordcount -m 6 -r 2 inputfile outoutdir then I submit it.when it runs,the map tasks are all completes,but the reduce task do not run at all! I checked the log of JobTracker,finding the error:
>     at java.util.Hashtable.get(Hashtable.java:334)
>     at org.apache.hadoop.mapred.ReduceTask$ReduceCopier.fetchOutput(ReduceTask.java:966)
>     at org.apache.hadoop.mapred.ReduceTask.run
>     at org.apache.hadoop.mapred.TaskTracker$Child.main()
> the machine just stoped there,I have to ctrl+c to stop the program.
> but when I use this instructon:bin/hadoop jar hadoop-0.15.3-examples.jar wordcount -m 2 -r 1 inputfile outoutdir
>    it runs successfully!
>    I do not konw why! I think the numbers of machines should be greater than mapTasks,so i set it 6.my machines number is 3.
>    Looking forward for your reply!
>                                                                                           4.22,2008
>                                                                                           xiaowei
>