Hadoop MapReduce is a software framework for easily writing
applications which process vast amounts of data (multi-terabyte data-sets)
in-parallel on large clusters (thousands of nodes) of commodity
hardware in a reliable, fault-tolerant manner.
The SUM() function is a more efficient way of adding up cells since it allows you to specify the first and last cell in a range of cells to be added up. The SUM() function then adds up all the cells from the start to the end of the range. It is particularly powerful because it can be used to add up millions of cells in a very short, simple formula.