Particles At eXascale on High Performance Computers (PAX-HPC)

Many recent breakthroughs would not have been possible without access to the most advanced supercomputers. For example, for the Chemistry Nobel Prize winners in 2013, supercomputers were used to develop powerful computing programs and software, to understand and predict complex chemical processes or for the Physics Nobel Prize in 2017 supercomputers helped to make complex calculations to detect hitherto theoretical gravitational waves.

The advent of exascale systems is the next dramatic step in this evolution. Exascale supercomputing will enable new scientific endeavour in wide areas of UK science, including advanced materials modelling, engineering and astrophysics. For instance, solving atomic and electronic structures with increasing realism to solve major societal challenges - quantum mechanically detailed simulation and steering design of batteries, electrolytic cells, solar cells, computers, lighting, and healthcare solutions, as well as enabling end-to-end simulation of transients (such as bird strike) in a jet engine, to simulation of tsunami waves over-running a series of defensive walls, or understanding the universe at a cosmological scale. Providing a level of detail to describe accurately these challenging problems can be achieved using particle-based models that interact in complicated dance that can be visualised or analysed to see how our model of nature would react in various situations. To model problems as complex as outlined the ways the particles interact must be flexible and tailored to the problem and vast quantities of particles are needed (and or complicated interactions). This proposal takes on the challenge of efficiently calculating the interacting particles on vast numbers of computer cores. The density of particles can be massively different at different locations, and it is imperative to find a way for the compute engines to have similar amounts of work - novel algorithms to distribute the work over different types of compute engines will be developed and used to develop and run frontier simulations of real-world challenges.

There is a high cost of both purchasing and running an exascale system, so it is imperative that appropriate software is developed before users gain access to exascale facilities. By definition, exascale supercomputers will be three orders of magnitude more powerful than current UK facilities, which will be achieved by a larger number of cores and the use of accelerators (based on gaming graphic cards, for example). This transition in computer power represents both an anticipated increase in hardware complexity and heterogeneity, and an increase in the volume of communication between cores that will hamper algorithms used on UK's current supercomputers. Many, if not all, of our software packages will require major changes before the hardware architectures can be fully exploited. The investigators of this project are internationally leading experts in developing (enabling new science) and optimising (making simulations more efficient) state-of-the-art particle-based software for running simulations on supercomputers, based here and abroad. Software that we have developed is used both in academia and in industry. In our project we will develop solutions and implement these in our software and, importantly, train Research Software Engineers to become internationally leading in the art of exploiting exascale supercomputers for scientific research.