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).
/benchmarks/streaming-21/hduser1/terasort/terasort-output Terasort has both map tasks and reduce tasks. The number of reduce tasks can be specified with mapred.reduce.tasks but the number of map tasks is automatically determined by dividing the total size of the input files by the HDFS block size. 1 TB (base 10) divided by 512 MiB (base 2) will give you 1863 map tasks.