Programming Models and MapReduce Quiz

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What are the two functions expressed by the user of the MapReduce library?

Map and Reduce.

What problem does the programming model consider?

Counting the number of occurrences of each word in a large collection of documents.

What does the Map function do?

Takes an input pair and produces a set of intermediate key/value pairs.

What does the Reduce function do?

Accepts an intermediate key and a set of values for that key, and merges together these values to form a possibly smaller set of values. Signup and view all the answers

How many output values are typically produced per Reduce invocation?

Typically just zero or one output value is produced per Reduce invocation. Signup and view all the answers

Explain the purpose of the Map function in the MapReduce programming model.

The Map function takes an input pair and produces a set of intermediate key/value pairs, grouping together all intermediate values associated with the same intermediate key. Signup and view all the answers

What is the role of the Reduce function in the MapReduce programming model?

The Reduce function accepts an intermediate key and a set of values for that key, merging them together to form a possibly smaller set of values. Signup and view all the answers

How does the MapReduce library handle the intermediate values in the MapReduce programming model?

The MapReduce library groups together all intermediate values associated with the same intermediate key and passes them to the Reduce function. Signup and view all the answers

What is the typical output of the Reduce function in the MapReduce programming model?

Typically, just zero or one output value is produced per Reduce invocation. Signup and view all the answers

For what purpose does the user write the Map and Reduce functions in the MapReduce programming model?

The user writes the Map function to process input pairs and produce intermediate key/value pairs, and the Reduce function to merge intermediate values together to form output values. Signup and view all the answers