Supercomputing: Experience With Operational Parallel Processing

Operational numerical weather prediction requires that all the computing power available is harnessed to the one task, otherwise the weather will have changed before it has been predicted. Therefore, in 1983 after the advent of multiprocessor systems as the most powerful computers, the European Centre for Medium-Range Weather Forecasts (ECMWF) undertook to modify its main algorithms and to run its forecast programs in multitasking mode. The decisions for achieving this goal, taken with regard to program structure and synchronization methods, will be discussed. The constraints imposed by the operational nature of the work will be highlighted. A set of requirements will be developed which will satisfy the needs of ECMWF and similar centres.