SANDeRS: Smart, Adaptive Compilation for Dark Silicon

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We live in an era of multi-cores: computing processors are no longer marketed by their clock speeds, they are marked by the number of cores. The fundamental limits of energy and power density of processors will soon push us further into an age of dark-silicon where only a small portion of the chip can be powered at any time. In such a setting, putting more of the same processing cores on a chip (i.e. homogeneity) gives no advantage. This has forced computer architects to introduce heterogeneous many-core systems built around distinct processors -- which have different energy and performance characteristics and each is specialised for a certain class of applications. Computer architects now hope that software will find ways to unlock the potential of heterogeneous many-cores. Software developers, however, are struggling to cope with this dramatic increase in complexity; and the current compiler tools, whose role is to enable software makes effective use of the underlying hardware, are simply inadequate to the task.It is already a daunting task to build optimising compilers for homogeneous multi-cores consisting of identical cores, even just targeting performance (i.e. to make programs faster). It typically takes several generations of a compiler to start to effectively exploit the processor's potential, by which time a new processor appears and the process starts again. It will be a fundamentally more difficult task to design efficient compiler heuristics for optimising energy (i.e. to reduce energy consumption) and performance on heterogeneous many-cores, especially given the subtle interactions of different cores and inter-connections. Even if successfully achieved, the task of compiler design must likely to be started again when moving to a new released processor. This never ending game of catch-up inevitably delays time to market, meaning that we rarely fully exploit the hardware in its lifetime. If no solution is found, we will be faced with software stagnation and will be unable to offer scalable computing performance -- a driving force that has dramatically changed our society over the past 50 years.What is needed is an approach that evolves and adapts to the future hardware architectural change and delivers scalable performance over hardware generations. This project offers precisely that. It will achieve this by bringing together two distinct areas of computer science: parallel compiler design and machine learning to develop a new paradigm for energy and performance optimisation. Our key insight is that the best optimisation strategies can be learned from similar software/hardware settings; and the learnt knowledge can be constantly refreshed without human involvement. This project will deliver such a smart, adaptive compilation system. We will use machine learning to acquire knowledge of workloads, applications and the underlying hardware, testing new compilation strategies, learning how each individual program should be optimised for each specific computing environment, and constantly improving the optimisation heuristics over time. As knowledge of the application environment grows, our system will make programs faster and more energy efficient; for example, software will respond quicker and the battery life will last longer on mobile phones. It will reduce time to market for software products and deliver scalable performance as hardware advances. If successful, such as programme of work will help to the looming software crisis of dark silicon, which will be of benefit to academics and UK industry, and system software researchers and developers worldwide.