Design and Development of Domain Specific Active Libraries with Proxy Applications

Representative applications are versatile tools to evaluate new programming approaches, techniques and optimisations as a way to ensure continued high performance on future computing architectures. They make experimentation much easier before adopting changes/insights into the large scientific codes. In this paper we demonstrate the important role played by representative/proxy applications in designing and developing two high-level programming approaches: namely the OP2 and OPS domain specific (active) libraries. OP2 and OPS utilizes code generation techniques to produce automatic parallelisations from a high-level abstract problem declaration. The strategy delivers significant developer productivity to the domain scientist, while at the same time allowing computational experts to adopt the latest programming models and hardware-specific optimisations into the library and code generation tools to achieve near optimal performance. We show how representative applications have been a cornerstone in the development of OP2 and OPS and chart our experiences. In particular, we demonstrate how the range of hand-tuned optimized parallelisations of the CloverLeaf hydrodynamics mini-app allowed us to gain clear evidence that the OPS based code generated parallelisations were indeed as optimal as the hand-tuned versions. Additionally, with the use of a representative application from the CFD domain we demonstrate how the optimisations discovered and applied to proxy apps are indeed directly transferable to a large-scale industrial application at Rolls Royce plc. These results provide significant evidence into the utility of representative applications to improve productivity, enable performance portability and ultimately future-proof scientific applications.