Lists a number of possible applications of MapReduce. Describe one other possible application and sketch out how this would be implemented in MapReduce, providing in particular outline implementations of the map and reduce functions.
What will be an ideal response?
There are a large number of possible answer to this question, but we provide one example, that is summing the elements of a large array.
The MapReduce framework will take this large array and split it into chunks passing the chunks on to parallel instances of the map operation.
This map operation will take its portion of the array and sum the elements in this portion, emitting the intermediary result. This result is a key-value pair. In this case, the key is not significant and will (say) be given the same value across all instances of map, say 1.
The reduce function then takes all intermediary results and produces the sum of all the values as the final result. In this case, only one instance of the reduce operation is required, seeking all intermediary results with the given key (1), and calculating the sum.
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