Dr Hook is software written by ECMWF to profile code. All new UM routines are required to have a call to dr_hook at the start and end of the routine (the only routines without dr_hook calls that I'm aware of is the COSP routines, which is apparently an old piece of code, which shouldn't be that important for this study). Dr Hook uses these calls to determine the time spent in each routine (self time), and the time spent in each routine plus all the routines it calls (total time), among other things for each PE - and stores this in files called drhook.prof.<PE number> where the <PE number> runs from 1 to the total number of PEs used. These files can be found in the main run directories.
These pages explain
