Top "Mapreduce" questions

MapReduce is an algorithm for processing huge datasets on certain kinds of distributable problems using a large number of nodes

When do reduce tasks start in Hadoop?

In Hadoop when do reduce tasks start? Do they start after a certain percentage (threshold) of mappers complete? If so, …

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Hadoop Streaming Job failed error in python

From this guide, I have successfully run the sample exercise. But on running my mapreduce job, I am getting the …

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hadoop map reduce secondary sorting

Can any one explain me how secondary sorting works in hadoop ? Why must one use GroupingComparator and how does it …

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What is Google's Dremel? How is it different from Mapreduce?

Google's Dremel is described here. What's the difference between Dremel and Mapreduce?

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How does Hadoop process records split across block boundaries?

According to the Hadoop - The Definitive Guide The logical records that FileInputFormats define do not usually fit neatly into …

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Calling a mapreduce job from a simple java program

I have been trying to call a mapreduce job from a simple java program in the same package.. I tried …

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Hadoop input split size vs block size

I am going through hadoop definitive guide, where it clearly explains about input splits. It goes like Input splits doesn’…

hadoop mapreduce
Hadoop DistributedCache is deprecated - what is the preferred API?

My map tasks need some configuration data, which I would like to distribute via the Distributed Cache. The Hadoop MapReduce …

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How to write 'map only' hadoop jobs?

I'm a novice on hadoop, I'm getting familiar to the style of map-reduce programing but now I faced a problem : …

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Simple Java Map/Reduce framework

Can anyone point me at a simple, open-source Map/Reduce framework/API for Java? There doesn't seem to much evidence …

java mapreduce