Consider the following pseudo code for mapreduce to find the frequency of words in a collection of documents:map(String key, String value)// key: document name// value: document contents for each word w in value   EmitIntermediate(w, 1)reduce(String key, Iterator values):// key: word// values: a list of counts  for each v in values:    result += ParseInt(v);    Emit(AsString(result));So the map step gets each word as a key and output its frequency in a document. Does the reduce step sum the counts of each word? 
MapReduce Pseudocode
algorithms;parallel computing