CCD-410 · Question #59
You have written a Mapper which invokes the following five calls to the OutputColletor.collect method: output.collect (new Text ("Apple"), new Text ("Red") ) ; output.collect (new Text ("Banana")…
The correct answer is B. 3. reduce() gets called once for each [key, (list of values)] pair. To explain, let's say you called: out.collect(new Text("Car"),new Text("Subaru"); out.collect(new Text("Car"),new Text("Honda"); out.collect(new Text("Car"),new Text("Ford"); out.collect(new Text("Truck"),new…
Question
You have written a Mapper which invokes the following five calls to the OutputColletor.collect method:
output.collect (new Text ("Apple"), new Text ("Red") ) ; output.collect (new Text ("Banana"), new Text ("Yellow") ) ; output.collect (new Text ("Apple"), new Text ("Yellow") ) ; output.collect (new Text ("Cherry"), new Text ("Red") ) ; output.collect (new Text ("Apple"), new Text ("Green") ) ; How many times will the Reducer's reduce method be invoked?
Options
- A6
- B3
- C1
- D0
- E5
How the community answered
(29 responses)- B83% (24)
- C10% (3)
- D3% (1)
- E3% (1)
Explanation
reduce() gets called once for each [key, (list of values)] pair. To explain, let's say you called: out.collect(new Text("Car"),new Text("Subaru"); out.collect(new Text("Car"),new Text("Honda"); out.collect(new Text("Car"),new Text("Ford"); out.collect(new Text("Truck"),new Text("Dodge"); out.collect(new Text("Truck"),new Text("Chevy"); Then reduce() would be called twice with the pairs reduce(Car, <Subaru, Honda, Ford>) reduce(Truck, <Dodge, Chevy>)
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