|Title||Report from the IFS scalability project|
|Publication Type||Technical memorandum|
|Secondary Title||ECMWF Technical Memorandum|
The scalability of the data assimilation system and forecast model at ECMWF is an area of growing concern. Current industry trends indicate that the core count on High Performance Computers will increase dramatically in the future and ECMWF must be ready to meet this challenge. Here we discuss the scaling properties of the main components of ECMWF's forecasting system and reach some tentative conclusions. The forecast model seem to scale reasonably well when trying to solve bigger problems on increasing number of cores. In contrast, the data assimilation system is only able to efficiently use a fairly small fraction of the High Performance Computer currently installed at ECMWF. It would seem that this is a fundamental feature of the algorithm used rather than a technical implementation issue. Any further improvement must come from a thorough review of the algorithms employed, adopting solutions that can be seen to scale to an order of magnitude more cores than currently employed.