Question

Under the MapReduce v1 programming model, which optional phase is executed simultaneously with the Shuffle phase?

A. Split
B. Map
C. Combiner
D. Reduce

Answer 1

C. Combiner The optional phase that runs alongside the Shuffle phase in MapReduce v1 is the Combiner phase, which is a local reduce operation to minimize the volume of data transferred during the Shuffle phase.

Step-by-step explanation:

Under the MapReduce v1 programming model, the optional phase that is executed simultaneously with the Shuffle phase is C. Combiner. The Combiner phase is a mini-reduce process that operates only on the data generated by the Map phase,

effectively performing a local reduce operation which can greatly reduce the amount of data that needs to be shuffled across the network to the Reduce phase.

It is important to note that not all MapReduce jobs will have a Combiner phase, as it is application-specific and its use depends on whether the reduce operation is commutative and associative, allowing for partial combining before the full reduction.