Microtasking as a complement to macrotasking

The ECMWF weather model runs daily as a time critical application. Acceptable elapsed times are achieved by multitasking the code on a CRAY X-MP/48. This is done at a high level giving rise to large tasks. Investigations have been carried out to tackle inefficiencies by microtasking at a low level so that the code can take advantage of any idle processors which may become available.