The first experiment was text processing word count
experiment to count the number of words that occur within a
set of large sized documents. The map function splits each
document into words and outputs each word together with the
digit "1." The output records are therefore of the form (word,
1). The MapReduce framework groups all the records with
the same key (i.e., word) and feeds them into the reduce
function. The reduce function sums the input values and
outputs the word and the total number of occurrences in the
document(s).