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courses:mapreduce-tutorial:step-8 [2012/01/25 14:46]
straka vytvořeno 		courses:mapreduce-tutorial:step-8 [2012/01/25 14:54]
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-====== MapReduce Tutorial : Multiple reducers and partitioning ======+====== MapReduce Tutorial : Multiple mappers, reducers and partitioning ====== 
 + 
 +In order to achieve parallelism, mappers and reducers must be executed in parallel. 
 + 
 +===== Multiple mappers ===== 
 +The number of mappers is determined automatically according to input files sizes. Every input file is divided into //splits//. The default split size is 32MB. Every file split is then executed by a different mapper. 
 + 
 +The size of file split can be overridden by ''mapred.min.split.size'' and ''maperd.max.split.size''. See the next tutorial step for how to set these flags. 
 + 
 +===== Multiple reducers ===== 
 + 

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