In a large MapReduce job with m mappers and n reducers, how many distinct copy operations will there be in the sort/shuffle phase?

In a large MapReduce job with m mappers and n reducers, how many distinct copy operations will there be in the sort/shuffle phase?
A . mXn (i.e., m multiplied by n)
B . n
C . m
D . m+n (i.e., m plus n)
E . mn (i.e., m to the power of n)

View Answer

Answer: A

Explanation:

A MapReduce job with m mappers and r reducers involves up to m * r distinct copy operations, since each mapper may have intermediate output going to every reducer.