MapReduce$]$ Consider as input files that look as follows.

List

parke

ice cream

parke

tofu

parke

tomatoes

jeff

tofu

jeff

broccoli

jeff

ice cream

eric

milk

$...$

$...$

Input

List

represents grocery lists for people. Assume the format of each

is key$-$value.

$($a$)$ Describe the difference between a Map task and a Reduce task in MapRe$-$

duce.

$(4$ Marks$)$

$($b$)$ Design a MapReduce job that outputs grocery item $($e$.$g$.,$ice cream$)$

as key and the count of the number of people as value $($e$.$g$.,2)$ who have

that item on their list. Describe what each map and reduce does by filling

in the blanks:

Mapper Procedure: $(4$ Marks$)$

Input:

$($What is the input?$)$

Output:

$($What is the key$-$value output $?)$

Reducer Procedure: $(4$ Marks$)$

Input:

$($What is the input?$)$

Output:

$($What is the key$-$value output $?$