Definition

MapReduce is a processing technique and a program model for distributed computing based on java. The MapReduce algorithm contains two important tasks, namely Map and Reduce.

• Map takes a set of data and converts it into another set of data, where individual elements are broken down into tuples (key/value pairs).
• Reduce task takes the output from a map as an input and combines those data tuples into a smaller set of tuples.

As the sequence of the name MapReduce implies, the reduce task is always performed after the map job.

Example code is in my project.