Earning Points. Starwood's Preferred Guest program is fairly straightforward: the more nights you spend at participating hotels, the faster you'll earn a free night.
As seen in the EXECUTING phase, the map will write (using Mapper.Context.write()) its output into a circular in-memory buffer (MapTask.MapOutputBuffer). The size of this buffer is fixed and determined by the configuration parameter mapreduce.task.io.sort.mb (default: 100MB).
MapReduce can be implemented in various languages. Java is the most common implementation, and is used for demonstration purposes in this document. Development languages. Languages or frameworks that are based on Java and the Java Virtual Machine can be ran directly as a MapReduce job. The example used in this document is a Java MapReduce application. Non-Java languages, such as C#, Python, or standalone executables, must use Hadoop streaming. Hadoop streaming communicates with the mapper and reducer over STDIN and STDOUT.