|| at May 17, 2010 at 4:45 am
For a reduce task, the execution is divided into three phases, each of which accounts for 1/3 of the score:
• The copy phase, when the task fetches map outputs.
• The sort phase, when map outputs are sorted by key.
• The reduce phase, when a user-defined function is applied to the list of map outputs with each key.
Yuan Panfeng(原攀峰) | BeiHang University
在2010-05-17 09:44:38，"stan lee" <email@example.com> 写道：
When I run the sort job, I found when there are 70 reduce tasks running and
no one completed, the progress bar shows that it has finished about 80%, so
how the mapreduce mechnism to caculate this?
Also, when I run a job, as we know, we can determine the number of total
reduce tasks through setNumReduceTasks() function, but how to determine the
reducer number(I mean the tasktracker number which run the reduce task)