SOFTWARE ENGINEERING

Detailed explanation-1: -Mapper::map Users can customize the map function to process the input data. The input data are transformed into some intermediate key/value pairs.

Detailed explanation-2: -The Mapper processes the input is the (key, value) pairs and provides an output as (key, value) pairs. The output from the Mapper is called the intermediate output. The Mapper may use or ignore the input key. For example, a standard pattern is to read a file one line at a time.

Detailed explanation-3: -MapReduce is a programming model for processing and generating large data sets. Users specify a map function that processes a key/value pair to generate a set of intermediate key/value pairs, and a reduce function that merges all intermediate values associated with the same intermediate key.