Incorrect systems: It's not the problem, It's the solution

We present an overview of state-of-the-art work in the engineering of digital systems (hardware and software) where traditional correctness requirements are relaxed, usually for higher performance and lower resource consumption but possibly also for other non-functional properties such as more robustness and less cost. The work presented here is categorized into work that involves just hardware, hardware and software, and just software. In particular, we discuss work on probabilistic and approximate design of processors, unreliable cores in asymmetric multi-core architectures, best-effort computing, stochastic processors, accuracy-aware program transformations, and relaxed concurrent data structures. As common theme we identify, at least intuitively, “metrics of correctness” in each piece of work which appear to be important for understanding the effects of relaxed correctness requirements and their relationship to performance improvements and resource consumption.