ADApprox - Towards Application-Driven Approximate Logic Synthesis

Across the computing landscape, many application domains are resilient, to a degree, towards lossy optimisations. Nonetheless, traditional electronics systems design practices, if at all considering the effect of approximations, are only concerned with ensuring that the correctness of an application outcome is not overly affected by quantisation errors. The emergence of the Approximate Computing (AC) paradigm challenges this stance, adopting instead aggressive tailoring strategies as a major avenue towards the maximisation of the performance and efficiency of computing systems. AC postulates that systems can be customised for a particular application field across three dimensions: run-time performance (latency or throughput), employed resources (area, energy) and Quality- of-Service (QoS). Moreover, AC states that these three metrics can be effectively traded-off against each other to accommodate different requirements. AC offers a path towards a sustained increase in computational performance independently of the low- level characteristic of the transistors used to implement digital integrated circuits. AC avenues are therefore nowadays of increasing relevance against a backdrop of diminishing returns from technology scaling, both in terms of operating frequencies and of energy efficiencies. Nonetheless, recent headways in AC have, for the most part, adopted a compartmentalised approach, offering solutions covering single abstraction levels (e.g., methodologies for approximate circuit synthesis, architectures, compiler-level transformations). The ambition at the foundation of the ADApprox project is instead to explore their synergies, developing a conceptual strategy, as well as a prototype framework embodying it, able to judiciously harness approximation opportunities while spanning multiple hardware and software layers. I plan to assess the benefits of the ADApprox approach on state of the art heterogeneous systems comprising software-programmable processors and hardware accelerators realised on reconfigurable logic. Such platforms, termed Systems on Programmable Chips (SoPCs), are becoming increasingly popular in a variety of scenarios, thanks to their high performance and flexibility. This latter characteristic, in turn, makes them ideal candidates for a holistic assessment of the benefits deriving from an AC stance.