Users want mobile devices that appear fast and responsive, but at the same time have long lasting batteries and do not overheat. Achieving both of these at once is difficult. The workloads employed to evaluate mobile optimisations are rarely representative of real mobile applications and are oblivious to user perception, focussing only on performance. As a result hardware and software designers' decisions do not respect the user's Quality of Experience (QoE). The device either runs faster than necessary for optimal QoE, wasting energy, or the device runs too slowly, spoiling QoE. SUMMER will develop the first framework to record, replay, and analyse mobile workloads that represent and measure real user experience. Our work will expose for the first time the real Pareto trade-off between the user's QoE and energy consumption. The results of this project will permit others, from computer architects up to library developers, to make their design decisions with QoE as their optimisation target. To show the power of this new approach, we will design the first energy efficient operating system scheduler for heterogeneous mobile processors which takes QoE into account. With heterogeneous mobile processors just now entering the market, a scheduler able to use them optimally is urgently needed. We expect our scheduler to be at least 50% more energy efficient on average than the standard Linux scheduler on an ARM BIG.LITTLE system.

The computational demands of modern computer applications make the pursuit of high performance more critical than ever, and mobile, battery-powered devices, as well as concerns related to climate change, require high performance to co-exist with energy-efficiency. Due to physical limits, the traditional means for improving hardware performance by increasing processor frequency now carries an unacceptably high energy cost. Advances in processor fabrication technology instead allow the construction of many-core processors, where hundreds or thousands of processing elements are placed on a single chip, promising high performance and energy-efficiency through sheer volume of processing elements. Many-core devices are present in practically all consumer devices, including smartphones and tablets. As a result, the general public in developed countries interact with many-core software daily. Many-core technology is also used to accelerate safety-critical software in domains such as medical imaging and autonomous vehicle navigation. It is thus important that many-core software should be reliable. This requires reliable software from programmers, but also a reliable "stack" to support this software, including compilers that allow software to execute on many-core devices, and the many-core devices themselves. Recent work on formal verification and testing by myself and other researchers has identified serious technical problems spanning the many-core stack. These problems undermine confidence in applications of many-core technology: defective many-core software could risk fatal accidents in critical domains, and impact negatively on users in other important application areas. My long-term vision is that the reliability of many-core programming can be transformed through breakthroughs in programming language specification, formal verification and test case generation, enabling automated tools to assist programmers and platform vendors in constructing reliable many-core applications and language implementations. The aim of this five-year Fellowship is to undertake foundational research to investigate a number of open problems whose solution is key to enabling this long-term vision. First, I seek to investigate whether it is possible to precisely express the intricacies of many-core programming language using formal mathematics, providing a rigorous basis on which software and language implementations can be constructed. Second, I aim to tackle several open problems that stand in the way of effective formal verification of many-core software, which would allow developers to obtain strong guarantees that such software will operate as required. Third, I will investigate raising this level of rigour beyond many-core languages. A growing trend is for applications to be written in relatively simple, high-level representations, and then automatically translated into high-performance many-core code. This translation process must preserve the meaning of programs; I will investigate methods for formally certifying that it does. Fourth, I will formulate new methods for testing many-core language implementations, exploiting the rigorous language definitions brought by my approach to enable high test coverage of subtle language features. Collectively, progress on these problems promises to enable a *high-assurance* many-core stack. I will demonstrate one instance of such a stack for the industry-standard OpenCL language and the PENCIL high-level language, showing that high-level PENCIL programs can be reliably compiled into rigorously-defined OpenCL, integrated with verified library components, and deployed on thoroughly tested implementations from many-core vendors. Partnership with four leading many-core technology vendors, AMD, ARM, Imagination Technologies and NVIDIA, provides excellent opportunities for the advances the Fellowship makes to have broad industrial impact.

High Performance Embedded and Distributed Systems (HiPEDS), ranging from implantable smart sensors to secure cloud service providers, offer exciting benefits to society and great opportunities for wealth creation. Although currently UK is the world leader for many technologies underpinning such systems, there is a major threat which comes from the need not only to develop good solutions for sharply focused problems, but also to embed such solutions into complex systems with many diverse aspects, such as power minimisation, performance optimisation, digital and analogue circuitry, security, dependability, analysis and verification. The narrow focus of conventional UK PhD programmes cannot bridge the skills gap that would address this threat to the UK's leadership of HiPEDS. The proposed Centre for Doctoral Training (CDT) aims to train a new generation of leaders with a systems perspective who can transform research and industry involving HiPEDS. The CDT provides a structured and vibrant training programme to train PhD students to gain expertise in a broad range of system issues, to integrate and innovate across multiple layers of the system development stack, to maximise the impact of their work, and to acquire creativity, communication, and entrepreneurial skills. The taught programme comprises a series of modules that combine technical training with group projects addressing team skills and system integration issues. Additional courses and events are designed to cover students' personal development and career needs. Such a comprehensive programme is based on aligning the research-oriented elements of the training programme, an industrial internship, and rigorous doctoral research. Our focus in this CDT is on applying two cross-layer research themes: design and optimisation, and analysis and verification, to three key application areas: healthcare systems, smart cities, and the information society. Healthcare systems cover implantable and wearable sensors and their operation as an on-body system, interactions with hospital and primary care systems and medical personnel, and medical imaging and robotic surgery systems. Smart cities cover infrastructure monitoring and actuation components, including smart utilities and smart grid at unprecedented scales. Information society covers technologies for extracting, processing and distributing information for societal benefits; they include many-core and reconfigurable systems targeting a wide range of applications, from vision-based domestic appliances to public and private cloud systems for finance, social networking, and various web services. Graduates from this CDT will be aware of the challenges faced by industry and their impact. Through their broad and deep training, they will be able to address the disconnect between research prototypes and production environments, evaluate research results in realistic situations, assess design tradeoffs based on both practical constraints and theoretical models, and provide rapid translation of promising ideas into production environments. They will have the appropriate systems perspective as well as the vision and skills to become leaders in their field, capable of world-class research and its exploitation to become a global commercial success.