Question

Under the Map Reduce v1 programming model, what happens in a "Reduce" step?

A. Worker nodes process pieces in parallel.
B. Input is split into pieces.
C. Worker nodes store results on their own local file systems.
D. Data is aggregated by worker nodes.

Answer 1

In the Reduce step of MapReduce programming, worker nodes aggregate data to form a smaller, combined output, such as totaling counts from a Map step.

Step-by-step explanation:

Under the MapReduce v1 programming model, during the Reduce step, the data is aggregated by worker nodes. This phase takes the output from the Map step, which is sorted and often shuffled across the nodes, and combines the data to form a smaller, combined output. For example, if the Map step counts the number of times a word appears across many documents, the Reduce step takes these counts and combines them to produce a total count for each word.