This paper describes the HW-Hume level of the novel Hume language. HW-Hume is the simplest subset of Hume that we have identified. It provides strong formal properties but posseses limited abstraction capabilities. In this paper, we introduce HW-Hume, show some simple example programs, describe an eÆcient software implementation, and demonstrate how important properties can be exposed as part of an integrated formally-based verification approach.

Abstract. This chapter describes Hume: a functionally-based language for programming with bounded resource usage, including time and space properties. The purpose of the Hume language design is to explore the expressibility/costability spectrum in resource-constrained systems, such as real-time embedded or control systems. It is unusual in being based on a combination of λ-calculus and finite state machine notions, rather than the more usual propositional logic, or flat finite-state-machine models. The use of a strict, purely functional programming notation allows the construction of a strong cost model for expressions, which can then be embedded into a simple cost model for processes. In this chapter, we introduce Hume, describe the Hume Abstract Machine implementation, and show how a high-level cost model can be constructed that relates costs from the abstract machine to Hume source programs. We illustrate our approach with an example adapted from the literature: a simple vending machine controller. 1

This paper describes ongoing work aimed at the construction of formal cost models and analyses that are capable of producing verifiable guarantees of resource usage (space, time and ultimately power consumption) in the context of real-time embedded systems. Our work is conducted in terms of the domain-specific language Hume, a language that combines functional programming for computations with finite-state automata for specifying reactive systems. We describe an approach in which high-level information derived from source-code analysis can be combined with worst-case execution time information obtained from abstract interpretation of low-level binary code. This abstract interpretation on the machine-code level is capable of dealing with complex architectural effects including cache and pipeline properties in an accurate way. It has been applied to several large-scale commercial safety-critical systems, including the flight control system for the Airbus A380. 1

Abstract. Hume is a novel language in the functional tradition, strongly oriented to systems requiring strong guarantees that resource bounds are met. To facilitate resource assurance, Hume enforces a separation of coordination and computation concerns, and deploys an abstract machine intermediary between implementations and analyses. These core design decisions also enable a high degree of portability across architectures and suit Hume well to multi-processor implementations. This papers machines. Initial results from experimental implementations are discussed and the design of a novel FPGA architecture tailored to Hume coordination is presented. Keywords: FPGA; embedded system; Hume. 1

Abstract. The formally motivated Hume language, based on the coordination of concurrent automata performing functional computations, was designed to support the development of systems requiring strong assurance that resource bounds are met. mHume is an experimental subset oriented to exploration of efficient heterogeneous multi-processors implementations. In this paper, the deployment of mHume on the FPGA MicroBlaze architecture is discussed. Preliminary results suggest very fast performance and good scalability compared with stock multi-core processors. Keywords: Hume, FPGA. 1