80 research outputs found

    Open Source Law, Policy and Practice

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    This book examines various policies, including the legal and commercial aspects of the Open Source phenomenon. Here, ‘Open Source’ is adopted as convenient shorthand for a collection of diverse users and communities, whose differences can be as great as their similarities. The common thread is their reliance on, and use of, law and legal mechanisms to govern the source code they write, use, and distribute. The central fact of open source is that maintaining control over source code relies on the existence and efficacy of intellectual property (‘IP’) laws, particularly copyright law. Copyright law is the primary statutory tool that achieves the end of openness, although implemented through private law arrangements at varying points within the software supply chain. This dependent relationship is itself a cause of concern for some philosophically in favour of ‘open’, with some predicting (or hoping) that the free software movement will bring about the end of copyright as a means for protecting software

    Programming Languages and Systems

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    This open access book constitutes the proceedings of the 31st European Symposium on Programming, ESOP 2022, which was held during April 5-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 21 regular papers presented in this volume were carefully reviewed and selected from 64 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

    Vectorization system for unstructured codes with a Data-parallel Compiler IR

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    With Dennard Scaling coming to an end, Single Instruction Multiple Data (SIMD) offers itself as a way to improve the compute throughput of CPUs. One fundamental technique in SIMD code generators is the vectorization of data-parallel code regions. This has applications in outer-loop vectorization, whole-function vectorization and vectorization of explicitly data-parallel languages. This thesis makes contributions to the reliable vectorization of data-parallel code regions with unstructured, reducible control flow. Reducibility is the case in practice where all control-flow loops have exactly one entry point. We present P-LLVM, a novel, full-featured, intermediate representation for vectorizers that provides a semantics for the code region at every stage of the vectorization pipeline. Partial control-flow linearization is a novel partial if-conversion scheme, an essential technique to vectorize divergent control flow. Different to prior techniques, partial linearization has linear running time, does not insert additional branches or blocks and gives proved guarantees on the control flow retained. Divergence of control induces value divergence at join points in the control-flow graph (CFG). We present a novel control-divergence analysis for directed acyclic graphs with optimal running time and prove that it is correct and precise under common static assumptions. We extend this technique to obtain a quadratic-time, control-divergence analysis for arbitrary reducible CFGs. For this analysis, we show on a range of realistic examples how earlier approaches are either less precise or incorrect. We present a feature-complete divergence analysis for P-LLVM programs. The analysis is the first to analyze stack-allocated objects in an unstructured control setting. Finally, we generalize single-dimensional vectorization of outer loops to multi-dimensional tensorization of loop nests. SIMD targets benefit from tensorization through more opportunities for re-use of loaded values and more efficient memory access behavior. The techniques were implemented in the Region Vectorizer (RV) for vectorization and TensorRV for loop-nest tensorization. Our evaluation validates that the general-purpose RV vectorization system matches the performance of more specialized approaches. RV performs on par with the ISPC compiler, which only supports its structured domain-specific language, on a range of tree traversal codes with complex control flow. RV is able to outperform the loop vectorizers of state-of-the-art compilers, as we show for the SPEC2017 nab_s benchmark and the XSBench proxy application.Mit dem Ausreizen des Dennard Scalings erreichen die gewohnten Zuwächse in der skalaren Rechenleistung zusehends ihr Ende. Moderne Prozessoren setzen verstärkt auf parallele Berechnung, um den Rechendurchsatz zu erhöhen. Hierbei spielen SIMD Instruktionen (Single Instruction Multiple Data), die eine Operation gleichzeitig auf mehrere Eingaben anwenden, eine zentrale Rolle. Eine fundamentale Technik, um SIMD Programmcode zu erzeugen, ist der Einsatz datenparalleler Vektorisierung. Diese unterliegt populären Verfahren, wie der Vektorisierung äußerer Schleifen, der Vektorisierung gesamter Funktionen bis hin zu explizit datenparallelen Programmiersprachen. Der Beitrag der vorliegenden Arbeit besteht darin, ein zuverlässiges Vektorisierungssystem für datenparallelen Code mit reduziblem Steuerfluss zu entwickeln. Diese Anforderung ist für alle Steuerflussgraphen erfüllt, deren Schleifen nur einen Eingang haben, was in der Praxis der Fall ist. Wir präsentieren P-LLVM, eine ausdrucksstarke Zwischendarstellung für Vektorisierer, welche dem Programm in jedem Stadium der Transformation von datenparallelem Code zu SIMD Code eine definierte Semantik verleiht. Partielle Steuerfluss-Linearisierung ist ein neuer Algorithmus zur If-Conversion, welcher Sprünge erhalten kann. Anders als existierende Verfahren hat Partielle Linearisierung eine lineare Laufzeit und fügt keine neuen Sprünge oder Blöcke ein. Wir zeigen Kriterien, unter denen der Algorithmus Steuerfluss erhält, und beweisen diese. Steuerflussdivergenz induziert Divergenz an Punkten zusammenfließenden Steuerflusses. Wir stellen eine neue Steuerflussdivergenzanalyse für azyklische Graphen mit optimaler Laufzeit vor und beweisen deren Korrektheit und Präzision. Wir verallgemeinern die Technik zu einem Algorithmus mit quadratischer Laufzeit für beliebiege, reduzible Steuerflussgraphen. Eine Studie auf realistischen Beispielgraphen zeigt, dass vergleichbare Techniken entweder weniger präsize sind oder falsche Ergebnisse liefern. Ebenfalls präsentieren wir eine Divergenzanalyse für P-LLVM Programme. Diese Analyse ist die erste Divergenzanalyse, welche Divergenz in stapelallokierten Objekten unter unstrukturiertem Steuerfluss analysiert. Schließlich generalisieren wir die eindimensionale Vektorisierung von äußeren Schleifen zur multidimensionalen Tensorisierung von Schleifennestern. Tensorisierung eröffnet für SIMD Prozessoren mehr Möglichkeiten, bereits geladene Werte wiederzuverwenden und das Speicherzugriffsverhalten des Programms zu optimieren, als dies mit Vektorisierung der Fall ist. Die vorgestellten Techniken wurden in den Region Vectorizer (RV) für Vektorisierung und TensorRV für die Tensorisierung von Schleifennestern implementiert. Wir zeigen auf einer Reihe von steuerflusslastigen Programmen für die Traversierung von Baumdatenstrukturen, dass RV das gleiche Niveau erreicht wie der ISPC Compiler, welcher nur seine strukturierte Eingabesprache verarbeiten kann. RV kann schnellere SIMD-Programme erzeugen als die Schleifenvektorisierer in aktuellen Industriecompilern. Dies demonstrieren wir mit dem nab_s benchmark aus der SPEC2017 Benchmarksuite und der XSBench Proxy-Anwendung

    Proceedings of the 21st Conference on Formal Methods in Computer-Aided Design – FMCAD 2021

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    The Conference on Formal Methods in Computer-Aided Design (FMCAD) is an annual conference on the theory and applications of formal methods in hardware and system verification. FMCAD provides a leading forum to researchers in academia and industry for presenting and discussing groundbreaking methods, technologies, theoretical results, and tools for reasoning formally about computing systems. FMCAD covers formal aspects of computer-aided system design including verification, specification, synthesis, and testing

    Neolithic land-use in the Dutch wetlands: estimating the land-use implications of resource exploitation strategies in the Middle Swifterbant Culture (4600-3900 BCE)

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    The Dutch wetlands witness the gradual adoption of Neolithic novelties by foraging societies during the Swifterbant period. Recent analyses provide new insights into the subsistence palette of Middle Swifterbant societies. Small-scale livestock herding and cultivation are in evidence at this time, but their importance if unclear. Within the framework of PAGES Land-use at 6000BP project, we aim to translate the information on resource exploitation into information on land-use that can be incorporated into global climate modelling efforts, with attention for the importance of agriculture. A reconstruction of patterns of resource exploitation and their land-use dimensions is complicated by methodological issues in comparing the results of varied recent investigations. Analyses of organic residues in ceramics have attested to the cooking of aquatic foods, ruminant meat, porcine meat, as well as rare cases of dairy. In terms of vegetative matter, some ceramics exclusively yielded evidence of wild plants, while others preserve cereal remains. Elevated δ15N values of human were interpreted as demonstrating an important aquatic component of the diet well into the 4th millennium BC. Yet recent assays on livestock remains suggest grazing on salt marshes partly accounts for the human values. Finally, renewed archaeozoological investigations have shown the early presence of domestic animals to be more limited than previously thought. We discuss the relative importance of exploited resources to produce a best-fit interpretation of changing patterns of land-use during the Middle Swifterbant phase. Our review combines recent archaeological data with wider data on anthropogenic influence on the landscape. Combining the results of plant macroremains, information from pollen cores about vegetation development, the structure of faunal assemblages, and finds of arable fields and dairy residue, we suggest the most parsimonious interpretation is one of a limited land-use footprint of cultivation and livestock keeping in Dutch wetlands between 4600 and 3900 BCE.NWOVidi 276-60-004Human Origin

    Taphonomy, environment or human plant exploitation strategies?: Deciphering changes in Pleistocene-Holocene plant representation at Umhlatuzana rockshelter, South Africa

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    The period between ~40 and 20 ka BP encompassing the Middle Stone Age (MSA) and Later Stone Age (LSA) transition has long been of interest because of the associated technological change. Understanding this transition in southern Africa is complicated by the paucity of archaeological sites that span this period. With its occupation sequence spanning the last ~70,000 years, Umhlatuzana Rock Shelter is one of the few sites that record this transition. Umhlatuzana thus offers a great opportunity to study past environmental dynamics from the Late Pleistocene (MIS 4) to the Late Holocene, and past human subsistence strategies, their social organisation, technological and symbolic innovations. Although organic preservation is poor (bones, seeds, and charcoal) at the site, silica phytoliths preserve generally well throughout the sequence. These microscopic silica particles can identify different plant types that are no longer visible at the site because of decomposition or burning to a reliable taxonomical level. Thus, to trace site occupation, plant resource use, and in turn reconstruct past vegetation, we applied phytolith analyses to sediment samples of the newly excavated Umhlatuzana sequence. We present results of the phytolith assemblage variability to determine change in plant use from the Pleistocene to the Holocene and discuss them in relation to taphonomical processes and human plant gathering strategies and activities. This study ultimately seeks to provide a palaeoenvironmental context for modes of occupation and will shed light on past human-environmental interactions in eastern South Africa.NWOVidi 276-60-004Human Origin

    Theory and Practice of Cryptography and Network Security Protocols and Technologies

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    In an age of explosive worldwide growth of electronic data storage and communications, effective protection of information has become a critical requirement. When used in coordination with other tools for ensuring information security, cryptography in all of its applications, including data confidentiality, data integrity, and user authentication, is a most powerful tool for protecting information. This book presents a collection of research work in the field of cryptography. It discusses some of the critical challenges that are being faced by the current computing world and also describes some mechanisms to defend against these challenges. It is a valuable source of knowledge for researchers, engineers, graduate and doctoral students working in the field of cryptography. It will also be useful for faculty members of graduate schools and universities

    Ways and Capacity in Archaeological Data Management in Serbia

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    Over the past year and due to the COVID-19 pandemic, the entire world has witnessed inequalities across borders and societies. They also include access to archaeological resources, both physical and digital. Both archaeological data creators and users spent a lot of time working from their homes, away from artefact collections and research data. However, this was the perfect moment to understand the importance of making data freely and openly available, both nationally and internationally. This is why the authors of this paper chose to make a selection of data bases from various institutions responsible for preservation and protection of cultural heritage, in order to understand their policies regarding accessibility and usage of the data they keep. This will be done by simple visits to various web-sites or data bases. They intend to check on the volume and content, but also importance of the offered archaeological heritage. In addition, the authors will estimate whether the heritage has adequately been classified and described and also check whether data is available in foreign languages. It needs to be seen whether it is possible to access digital objects (documents and the accompanying metadata), whether access is opened for all users or it requires a certain hierarchy access, what is the policy of usage, reusage and distribution etc. It remains to be seen whether there are public API or whether it is possible to collect data through API. In case that there is a public API, one needs to check whether datasets are interoperable or messy, requiring data cleaning. After having visited a certain number of web-sites, the authors expect to collect enough data to make a satisfactory conclusion about accessibility and usage of Serbian archaeological data web bases

    From Clerks to Corpora: essays on the English language yesterday and today

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    Why is the Isle of Dogs in the Thames called Isle of Dogs? Did King Canute’s men bring English usage back to Jutland? How can we find out where English speakers suck their breath in to give a short response? And what did the Brontës do about dialect and think about foreign languages? The answers are in this collection of empirical work on English past and present in honour of Nils-Lennart Johannesson, Professor of English Language at Stockholm University. The first five chapters report individual studies forming an overview of current issues in the study of Old and Middle English phonology, lexis and syntax. The next six look at Early Modern and Modern English from a historical point of view, using data from corpora, manuscript archives, and fiction. Two more look at the Old English scholar JRR Tolkien and his work. The remaining chapters discuss aspects of Modern English. Several use corpora to look at English usage in itself or in relation to Swedish, French, or Norwegian. The last three look at grammatical models, the pragmatics of second language use, and modern English semantics
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