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courses:mapreduce-tutorial:step-31 [2012/02/06 08:13]
straka
courses:mapreduce-tutorial:step-31 [2012/02/06 08:21]
straka
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 It is crucial that all the mappers run simultaneously. This can be achieved using the ''/net/projects/hadoop/bin/compute-splitsize'' script: for given Hadoop input and requested number of mappers, it computes the appropriate splitsize. It is crucial that all the mappers run simultaneously. This can be achieved using the ''/net/projects/hadoop/bin/compute-splitsize'' script: for given Hadoop input and requested number of mappers, it computes the appropriate splitsize.
 +
 +When the computation finishes, only one of the mappers should print the results, as all of them have the same results. For simplicity, the ''cooperate'' method has ''boolean shouldWrite'' argument, which is set in exactly one mapper.
  
 ===== Example ===== ===== Example =====
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 </code> </code>
  
-You can run the example using: +You can run the example locally using: 
-  wget +  wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_export/code/courses:mapreduce-tutorial:step-31?codeblock=0' -O Sum.java 
 +  make -f /net/projects/hadoop/java/Makefile Sum.java 
 +  rm -rf step-31-out; /net/projects/hadoop/bin/hadoop Sum.jar /net/projects/hadoop/examples/inputs/numbers-small step-31-out 
 +  less step-31-out/part-* 
 +  
 +To run on a cluster with //C// machines using //C// mappers: 
 +  rm -rf step-31-out; /net/projects/hadoop/bin/hadoop -c C `/net/projects/hadoop/bin/compute-splitsize /net/projects/hadoop/examples/inputs/numbers-small C` Sum.jar /net/projects/hadoop/examples/inputs/numbers-small step-31-out 
 +  less step-31-out/part-* 
 + 
 +===== Exercise 1 =====
  
 +Implement an AllReduce job on 

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