title: What happens if I don't set 'number of reduce tasks' in my mapreduce program?
body: <p>I want to know what will happen if I don't include the <code>setNumReduceTasks()</code> in my mapreduce program's Driver class at all. What default value would it take?</p>
  
  <p>Once I wrote a MapReduce Java program and didn't <code>setNumReduceTasks()</code> in my code. But the monitoring app still showed many Reducers running.</p>
  
  <p>Why is this?</p>