Safe code transfromations for speculative execution in real-time systems

Although compiler optimization techniques are standard and successful in non-real-time systems, if naively applied, they can destroy safety guarantees and deadlines in hard real-time systems. For this reason, real-time systems developers have tended to avoid automatic compiler optimization of their code. However, real-time applications in several areas have been growing substantially in size and complexity in recent years. This size and complexity makes it impossible for real-time programmers to write optimal code, and consequently indicates a need for compiler optimization. Recently researchers have developed or modified analyses and transformations to improve performance without degrading worst-case execution times. Moreover, these optimization techniques can sometimes transform programs which may not meet constraints/deadlines, or which result in timeouts, into deadline-satisfying programs. One such technique, speculative execution, also used for example in parallel computing and databases, can enhance performance by executing parts of the code whose execution may or may not be needed. In some cases, rollback is necessary if the computation turns out to be invalid. However, speculative execution must be applied carefully to real-time systems so that the worst-case execution path is not extended. Deterministic worst-case execution for satisfying hard real-time constraints, and speculative execution with rollback for improving average-case throughput, appear to lie on opposite ends of a spectrum of performance requirements and strategies. Deterministic worst-case execution for satisfying hard real-time constraints, and speculative execution with rollback for improving average-case throughput, appear to lie on opposite ends of a spectrum of performance requirements and strategies. Nonetheless, this thesis shows that there are situations in which speculative execution can improve the performance of a hard real-time system, either by enhancing average performance while not affecting the worst-case, or by actually decreasing the worst-case execution time. The thesis proposes a set of compiler transformation rules to identify opportunities for speculative execution and to transform the code. Proofs for semantic correctness and timeliness preservation are provided to verify safety of applying transformation rules to real-time systems. Moreover, an extensive experiment using simulation of randomly generated real-time programs have been conducted to evaluate applicability and profitability of speculative execution. The simulation results indicate that speculative execution improves average execution time and program timeliness. Finally, a prototype implementation is described in which these transformations can be evaluated for realistic applications

The Design of Creative Crowdwork – From Tools for Empowerment to Platform Capitalism

The thesis investigates the methods used in the contemporary crowdsourcing of creative crowdwork and in particular the succession of conflicting ideas and concepts that led to the development of dedi- cated, profit-oriented, online platforms after 2005 for the outsourcing of cognitive tasks and creative labour to a large and unspecified group of people via open calls on the internet. It traces the historic trajectory of the notion of the crowd as well as the development of tech- nologies for online collaboration, with a focus on the accompanying narratives in the form of a dis- course analysis. One focus of the thesis is the clash between the narrative of the empowerment of the individual user through digital tools and the reinvention of the concept of the crowd as a way to refer to users of online platforms in their aggregate form. The thesis argues that the revivification of the notion of the crowd is indicative of a power shift that has diminished the agency of the individual user and empowered the commercial platform providers who, in turn, take unfair advantage of the crowdworker. The thesis examines the workings and the rhetoric of these platforms by comparing the way they address the masses today with historic notions of the crowd, formed by authors like Gustave Le Bon, Sigmund Freud and Elias Canetti. Today’s practice of crowdwork is also juxtaposed with older, arguably more humanist, visions of distributed online collaboration, collective intelligence, free soft- ware and commons-based peer production. The study is a history of ideas, taking some of the utopian concepts of early online history as a vantage point from which to view current and, at times, dystopian applications of crowdsourced creative labour online. The goal is to better understand the social mech- anisms employed by the platforms to motivate and control the crowds they gather, and to uncover the parameters that define their structure as well as the scope for their potential redesign. At its core, the thesis offers a comparison of Amazon Mechanical Turk (2005), the most prominent and infamous example for so-called microtasking or cognitive piecework, with the design of platforms for contest-based creative crowdwork, in particular with Jovoto (2007) and 99designs (2008). The crowdsourcing of design work is organised in decidedly differently ways to other forms of digital labour and the question is why should that be so? What does this tell us about changes in the practice and commissioning of design and what are its effects on design as a profession? However, the thesis is not just about the crowdsourcing of design work: it is also about the design of crowdsourcing as a system. It is about the ethics of these human-made, contingent social systems that are promoted as the future of work. The question underlying the entire thesis is: can crowdsourcing be designed in a way that is fair and sustainable to all stakeholders? The analysis is based on an extensive study of literature from Design Studies, Media and Cul- ture Studies, Business Studies and Human-Computer Interaction, combined with participant observa- tion within several crowdsourcing platforms for design and a series of interviews with different stake- holders

Digital work in the planetary market

Many of the world’s most valuable companies rely on planetary networks of digital work that underpin their products and services. This important book examines implications for both work and workers when jobs are commodified and traded beyond local labor markets. For instance, Amazon’s contractors in Costa Rica, India, and Romania are paid to structure, annotate, and organize conversations captured by ‘Alexa’ to train Amazon’s speech recognition systems. Findings show that despite its planetary connections, labor remains geographically “sticky” and embedded in distinct contexts. The research emphasizes the globe-spanning nature of contemporary networks without resorting to an understanding of “the global” as a place beyond space.Aujourd’hui, de nombreux emplois peuvent être exercés depuis n’importe où. La technologie numérique et la connectivité Internet généralisée permettent à presque n’importe qui, n’importe où, de se connecter à n’importe qui d’autre pour communiquer et interagir à l’échelle planétaire. Ce livre examine les conséquences, tant pour le travail que pour les travailleurs, de la marchandisation et de l’échange des emplois au-delà des marchés du travail locaux. Allant au-delà du discours habituel sur la mondialisation « le monde est plat », les contributeurs examinent à la fois la transformation du travail lui-même et les systèmes, réseaux et processus plus larges qui permettent le travail numérique dans un marché planétaire, en offrant des perspectives empiriques et théoriques. Les contributeurs - des universitaires et des experts de premier plan issus de diverses disciplines - abordent une variété de questions, notamment la modération du contenu, les véhicules autonomes et les assistants vocaux. Ils se penchent d’abord sur la nouvelle expérience du travail et constatent que, malgré ses connexions planétaires, le travail reste géographiquement collé et intégré dans des contextes distincts. Ils examinent ensuite comment les réseaux planétaires de travail peuvent être cartographiés et problématisés, ils discutent de la multiplicité productive et de l’interdisciplinarité de la réflexion sur le travail numérique et ses réseaux et, enfin, ils imaginent comment le travail planétaire pourrait être réglementé. Les directeurs Mark Graham est professeur de géographie de l’Internet à l’Oxford Internet Institute et chargé de cours à l’Alan Turing Institute. Il est l’éditeur du livre Digital Economies at Global Margins (MIT Press et CRDI, 2019). Fabian Ferrari est un candidat au doctorat à l’Oxford Internet Institute