Question

the output of the shuffle operation goes into the mapper before going into the reducer. true or false?

Answer 1

the answer of this question is true'

Answer 2

Shuffling is the process of transferring the data from the mappers to the reducers, so I think it is obvious that it is necessary for the reducers, since otherwise, they wouldn't be able to have any input (or input from every mapper).

Shuffling can start even before the map phase has finished, to save some time.

I think the answer is true.