Structural Synthesis for GXW Specifications

We define the GXW fragment of linear temporal logic (LTL) as the basis for synthesizing embedded control software for safety-critical applications. Since GXW includes the use of a weak-until operator we are able to specify a number of diverse programmable logic control (PLC) problems, which we have compiled from industrial training sets. For GXW controller specifications, we develop a novel approach for synthesizing a set of synchronously communicating actor-based controllers. This synthesis algorithm proceeds by means of recursing over the structure of GXW specifications, and generates a set of dedicated and synchronously communicating sub-controllers according to the formula structure. In a subsequent step, 2QBF constraint solving identifies and tries to resolve potential conflicts between individual GXW specifications. This structural approach to GXW synthesis supports traceability between requirements and the generated control code as mandated by certification regimes for safety-critical software. Synthesis for GXW specifications is in PSPACE compared to 2EXPTIME-completeness of full-fledged LTL synthesis. Indeed our experimental results suggest that GXW synthesis scales well to industrial-sized control synthesis problems with 20 input and output ports and beyond.Comment: The long (including appendix) version being reviewed by CAV'16 program committee. Compared to the submitted version, one author (out of her wish) is moved to the Acknowledgement. (v2) Corrected typos. (v3) Add an additional remark over environment assumption and easy corner case

Synthesizing a Lego Forklift Controller in GR(1): A Case Study

Reactive synthesis is an automated procedure to obtain a correct-by-construction reactive system from a given specification. GR(1) is a well-known fragment of linear temporal logic (LTL) where synthesis is possible using a polynomial symbolic algorithm. We conducted a case study to learn about the challenges that software engineers may face when using GR(1) synthesis for the development of a reactive robotic system. In the case study we developed two variants of a forklift controller, deployed on a Lego robot. The case study employs LTL specification patterns as an extension of the GR(1) specification language, an examination of two specification variants for execution scheduling, traceability from the synthesized controller to constraints in the specification, and generated counter strategies to support understanding reasons for unrealizability. We present the specifications we developed, our observations, and challenges faced during the case study.Comment: In Proceedings SYNT 2015, arXiv:1602.0078

Confessions of a live coder

This paper describes the process involved when a live coder decides to learn a new musical programming language of another paradigm. The paper introduces the problems of running comparative experiments, or user studies, within the field of live coding. It suggests that an autoethnographic account of the process can be helpful for understanding the technological conditioning of contemporary musical tools. The author is conducting a larger research project on this theme: the part presented in this paper describes the adoption of a new musical programming environment, Impromptu, and how this affects the author’s musical practice

A Fast and Accurate Cost Model for FPGA Design Space Exploration in HPC Applications

Heterogeneous High-Performance Computing (HPC) platforms present a significant programming challenge, especially because the key users of HPC resources are scientists, not parallel programmers. We contend that compiler technology has to evolve to automatically create the best program variant by transforming a given original program. We have developed a novel methodology based on type transformations for generating correct-by-construction design variants, and an associated light-weight cost model for evaluating these variants for implementation on FPGAs. In this paper we present a key enabler of our approach, the cost model. We discuss how we are able to quickly derive accurate estimates of performance and resource-utilization from the design’s representation in our intermediate language. We show results confirming the accuracy of our cost model by testing it on three different scientific kernels. We conclude with a case-study that compares a solution generated by our framework with one from a conventional high-level synthesis tool, showing better performance and power-efficiency using our cost model based approach