how can i know the number of tasks of map,reduce ,shuffle?

[张建]

dear
       I'm sorry for my poor in English.
       I'm confused about something.
       Recently, i read a paper names "TeraByte Sort on Apache Hadoop"
which was written by Owen O'Malley.  And i see the graph "Running Tasks
Over Time" ,how can i know the tasks of map, reduce ,shuffle, merge at a
certain time ?
       Thank you for your help !