Owicki-Gries Reasoning for C11 Programs with Relaxed Dependencies (Extended Version)?
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UTP Semantics for Shared-State, Concurrent, Context-Sensitive Process Models
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by University of Limerick Institutional Repository UTP Semantics for Shared-State, Concurrent, Context-Sensitive Process Models Andrew Butterfield Anila Mjeda John Noll Lero @ TCD Lero @ TCD Lero @ UL School of Computer Science and Statistics School of Computer Science and Statistics Tierney Building Trinity College, Dublin 2, Ireland Trinity College, Dublin 2, Ireland University of Limerick Email: Andrew.Butterfi[email protected] Email: [email protected] Email: [email protected] Abstract—Process Modelling Language (PML) is a notation semantics for shared global state concurrency, as a way to for describing software development and business processes. It get a suitable semantics for strict and flexible PML, inspired takes the form of a shared-state concurrent imperative language by the work of Woodcock and Hughes on unifying parallel describing tasks as activities that require resources to start and provide resources when they complete. Its syntax covers programming (UTPP, [13]). We present both a formal seman- sequential composition, parallelism, iteration and choice, but tics for a “weak” interpretation of PML, as well as a unified without explicit iteration and choice conditions. It is intended theory of concurrent programs (UTCP) that will provide a to support a range of context-sensitive interpretations, from a baseline theory for modelling more “flexible” and “strong” rough guide for intended behaviour, to being very prescriptive interpretations of PML. Part of our contribution is extending about the order in which tasks must occur. We are using Unifying Theories of Programming (UTP) to model this range of semantic the UTP methodology to use non-homogenous relations that interpretations, with formal links between them, typically of the mix dynamic state-change (observations with before- and nature of a refinement. -
Domain Theory for Concurrency
Domain Theory for Concurrency Mikkel Nygaard Glynn Winskel BRICS∗ Computer Laboratory University of Aarhus University of Cambridge Abstract A simple domain theory for concurrency is presented. Based on a categorical model of linear logic and associated comonads, it highlights the role of linear- ity in concurrent computation. Two choices of comonad yield two expressive metalanguages for higher-order processes, both arising from canonical construc- tions in the model. Their denotational semantics are fully abstract with respect to contextual equivalence. One language derives from an exponential of linear logic; it supports a straightforward operational semantics with simple proofs of soundness and adequacy. The other choice of comonad yields a model of affine-linear logic, and a process language with a tensor operation to be under- stood as a parallel composition of independent processes. The domain theory can be generalised to presheaf models, providing a more refined treatment of nondeterministic branching. The article concludes with a discussion of a broader programme of research, towards a fully fledged domain theory for concurrency. 1 Introduction Denotational semantics and domain theory of Scott and Strachey provide a global mathematical setting for sequential computation, and thereby place programming languages in connection with each other; connect with the mathematical worlds of algebra, topology and logic; and inspire programming languages, type disciplines and methods of reasoning. In concurrent/distributed/interactive computation that global mathematical gui- dance is missing, and domain theory has had little direct influence on theories of concurrent computation. One reason is that classical domain theory has not scaled up to the more intricate models used there. -
Four Domains for Concurrency
Theoretical Computer Science 90 (1991) 127-149 127 Elsevier Four domains for concurrency J.W. de Bakker and J.H.A. Warmerdam* Centre for Mathematics and Computer Science, P.O. Box 4079, 1009 AB Amsterdam, The Netherlands Abstract Bakker, J.W. de, and J.H.A. Warmerdam, Four domains for concurrency, Theoretical Computer Science 90 (1991) 127-149. We give four domains for concurrency in a uniform way by means of domain equations. The domains are intended for modelling the four possible combinations of linear time versus branching time, and of interleaving versus noninterleaving concurrency. We use the linear time, noninter leaved domain to give operational and denotational semantics for a simple concurrent language with recursion, and prove that (} ~ ftl. Prologue Among the reasons to fondly remember my first IFIP Congress (New York, 1965), I recall a meeting with the late Professors Andrei Ershov and Aad van Wijngaarden, both then already famous scholars, who strongly encouraged me to continue my incipient work on programming language semantics. Among the reasons to somewhat embarrassedly remember the 6th MFCS meeting (Tatranska Lomnica, 1977), I recall a discussion with Andrei Ershov on my unsatis factory first steps towards an understanding of concurrency semantics and infinite behaviour (cf. [6]). The paper to follow reports on how we spent the 1980s in Amsterdam working to remedy this. Among the reasons to sadly remember my otherwise so enjoyable visit to Akademgorodok in the fall of 1988, I recall in sorrow the news about the mortal illness and death of Academician Andrei Ershov, eminent computer scientist and world specialist in programming. -
Contractions in Comparing Concurrency Semantics
Contractions in Comparing Concurrency Semantics J.N. Kok & J.J.M.M. Rutten Centre for Mathematics and Computer Science P.O. Box 4079, 1009 AB Amsterdam, The Netherlands We define for a simple concurrent imperative language both operational and denotational semantic models as fixed points of contractions on complete metric spaces. Next, we develop a general method for comparing different semantic models by relating their defining contractions and exploit ing the fact that contractions have a unique fixed point. 0. INTRODUCTION We present a study of a simple concurrent imperative language, called L 0 . We shall define an operational semantics Bo and a denotational semantics 0D0 for it and give a comparison of the two models. (We shall use the terms semantics and semantic model as synonyms.) This comparison is the main subject of our paper, rather than the specific nature of the language itself or the particular properties of its semantics. The language L 0 has been defined and studied already in much detail in [BMOZI,2] and [BKMOZ], on which we rely heavily. It belongs to the wide class of concurrent (parallel) imperative programming languages. We shall discuss parallel execution through interleaving (shuffie) of elementary actions. Further, L 0 contains constructs for sequential composition, local nondeterrninacy, and recursion. For our semantic definitions we shall use metric structures, rather than order-theoretic domains. The metric approach is particularly felicitous for problems where histories, computa tional traces and tree-like structures of some kind are essential. Moreover, it allows for the definition of the notion of contraction, which we discuss in more detail in a moment. -
A Lightweight Formal Method for the Prediction of Non-Functional System Properties
A Lightweight Formal Method for the Prediction of Non-Functional System Properties Der Technischen Fakultät der Universität Erlangen-Nürnberg zur Erlangung des Grades Doktor-Ingenieur vorgelegt von Jörg Barner Erlangen — 2005 Als Dissertation genehmigt von der Technischen Fakultät der Universität Erlangen-Nürnberg Tag der Einreichung: 20.06.2005 Tag der Promotion: 14.10.2005 Dekan: Prof. Dr.-Ing. Alfred Leipertz Berichterstatter: Prof. Dr. Fridolin Hofmann, Prof. Dr. Khalid Al-Begain Acknowledgments First of all, I would like to thank Prof. Dr. Fridolin Hofmann for supervising this dissertation and for the open environment he created together with Prof. Dr.-Ing. Wolfgang Schröder- Preikschat in our department which allowed me to finish this project. Furthermore, I am particularly grateful to Prof. Dr. Khalid Al-Begain, my co-promoter, whose interest in appli- cations and the encouraging feedback he gave were always a great pleasure. I owe a lot of thanks to Dr.-Ing. Gunter Bolch, my “Ana” research group leader for many inspiring discussions which helped me a lot to sharpen my thoughts on important issues and prevented me from losing my direction. Without the commitment that Björn Beutel and Patrick Wüchner exhibited during the preparation of their master theses some of the concepts presented in this dissertation would have remained purely theoretical. My former office mate Dr.-Ing. Michael Schröder proof-read various intermediate ver- sions of this dissertation. Together with him, Stephan Kösters supported me in the nerve- wracking final phase before submitting the thesis by doing some valuable last-minute proof- reading. It has been a lot of fun to work at the department for distributed systems and operat- ing systems with all the colleagues and students. -
Correctness and Full Abstraction of Metric Semantics for Concurrency
Correctness and full abstraction of metric semantics for concurrency J.J.M.M. Rutten Centre for Mathematics and Computer Science P.O. Box 4079, 1009 AB Amsterdam, The Netherlands ABSTRACT: Four different semantic models are given for a simple uniform programming language, containing constructs for parallel composition, global nondeterminism and com munication: linear semantics, failure semantics, readiness semantics, and branching semantics. The mathematical framework used consists of complete metric spaces. All models and operators are given as fixed points of suitably defined contractions. This allows for a uniform presentation and an easy comparison of these models. It is shown that the latter three semantics all are correct and that the failure semantics is fully abstract with respect to the linear semantics. Although these results are not new, we believe the unifor mity of the way they are presented here to be of some interest. KEY WORDS AND PHRASES: concurrency, complete metric spaces, contractions, operational semantics, denotational semantics, compositionality, correctness, full abstraction. CoNTENTS 1. Introduction 2. A simple language 3. Four operational models 3.1. Linear semantics 3.2. Branching semantics 3.3. Readiness semantics 3.4. Failure semantics 629 3.5. Some examples 3.6. Relating the different operational models 4. 1bree compositional models 5. Semantic equivalence 6. Correctness and full abstraction 7. Related work 8. References 9. Appendix: Mathematical definitions 1. INTRODUCTION The semantics of a uniform programming language e is studied, containing the following con structs: atomic actions, which are left uninterpreted and which can be either internal or commun ications; sequential composition, global nondetenninism and parallel composition; and recursion, modeled via the simultaneous declaration of statement variables. -
Modular, Compositional, and Executable Formal Semantics for LLVM IR
Modular, Compositional, and Executable Formal Semantics for LLVM IR YANNICK ZAKOWSKI, Inria, France CALVIN BECK, University of Pennsylvania, USA IRENE YOON, University of Pennsylvania, USA ILIA ZAICHUK, Taras Shevchenko National University of Kyiv, Ukraine VADIM ZALIVA, Carnegie Mellon University, USA STEVE ZDANCEWIC, University of Pennsylvania, USA This paper presents a novel formal semantics, mechanized in Coq, for a large, sequential subset of the LLVM IR. In contrast to previous approaches, which use relationally-specified operational semantics, this new semantics 67 is based on monadic interpretation of interaction trees, a structure that provides a more compositional approach to defining language semantics while retaining the ability to extract an executable interpreter. Our semantics handles many of the LLVM IR’s non-trivial language features and is constructed modularly in terms of event handlers, including those that deal with nondeterminism in the specification. We show how this semantics admits compositional reasoning principles derived from the interaction trees equational theory of weak bisimulation, which we extend here to better deal with nondeterminism, and we use them to prove that the extracted reference interpreter faithfully refines the semantic model. We validate the correctness ofthe semantics by evaluating it on unit tests and LLVM IR programs generated by HELIX. CCS Concepts: • Software and its engineering ! Semantics; Compilers; • Theory of computation ! Program verification; Denotational semantics. Additional Key Words and Phrases: Semantics, Monads, Coq, LLVM, Verified Compilation ACM Reference Format: Yannick Zakowski, Calvin Beck, Irene Yoon, Ilia Zaichuk, Vadim Zaliva, and Steve Zdancewic. 2021. Modular, Compositional, and Executable Formal Semantics for LLVM IR. Proc. ACM Program. Lang. 5, ICFP, Article 67 (August 2021), 30 pages. -
Sense and Reference in Semantics Examples
Sense And Reference In Semantics Examples Hassan tats vehemently while inextensible Sid naphthalises rebukingly or cooings vestigially. Leguminous and tight Aram unpinned her tooms haggis outguess and getter homologous. Which Waiter dirties so disposedly that Wyatt soar her tummies? These possibilities in sense and epistemic intensions associated sense in identifying the meanings The in language may turn play the examples in sense reference semantics and of language but they varied according to. Priming led to shorter planning times but actually speaking times. We understand these examples structure and sense is hesperus picks out that description above examples we might intuitively think that? This direction is straightforwardly plausible. Lexical Semantics Department our Second Language Studies. For example dictionaries often monetary the words black death white senses like In. Here are whether few. Recent work in neurolinguistics supports this proposal. One word relationships between names and in his going the! Sometimes said to senses is semantically related matters is not occur if different reference? We are some man hits the sentences, then it will the examples in! There from some semantic featuresproperties that feeling usually prototypical for a word The green of attributes that define a pile the family The sense include a. To senses of reference in my research interests lie in its referent as ways in mapping process produces an example proves that have different epistemic contexts. Many philosophers and linguists have sought to define the trunk of meaning. So may every epistemic possibility W, the epistemic intensions of these sentences are true. Monica Lewinsky illustrate this conception, as do several other words labels attached to objects for sale being a shop, or life found nor a paint color chart. -
Graph Rewriting for a Partial Ordering Semantics of Concurrent Constraint Programming*
Theoretical Computer Science 109 (1993) 225-256 225 Elsevier Graph rewriting for a partial ordering semantics of concurrent constraint programming* Montanari, U. and F. Rossi. Graph rewriting for a partial ordering semantics of concurrent constraint programming, Theoretical Computer Science 109 (1993) 225-256. The concurrent constraint logic programming framework extends both logic programming and concurrent logic programming in that a program consists of the concurrent execution of agents which add (i.e., “tell”) and check (i.e., “ask”) constraints on a shared set of variables, and whose behaviour is described by a set of clauses. This formulation is very genera1 and can be seen as a concurrent logic programming she11 which is parametrized w.r.t. the underlying constraint system. Graphs and graph grammars can be conveniently used to describe such a framework, and the modelling is so elegant and expressive that they provide what we believe is the most natural abstract machine for concurrent constraint programming. In fact. basic notions like the possibility of asking or telling a constraint into the shared store are very easy to express in the algebraic approach to graph rewriting. More precisely, the shared store is represented as a (hyper)graph, where nodes are variables and arcs are constraints or agents. Then. both the entailment relation of the underlying constraint system and the local behaviour of agents is expressed by suitable sets of graph produc- tions, which transform the current global state of the system into a new one. Finally, each computation is represented by a graph derivation. In our setting the shared store is not seen as one constraint, but as a set of constraints which possibly share variables. -
Modular Relaxed Dependencies in Weak Memory Concurrency⋆
Modular Relaxed Dependencies in Weak Memory Concurrency? Marco Paviotti12, Simon Cooksey2, Anouk Paradis3, Daniel Wright2, Scott Owens2, and Mark Batty2 1 Imperial College London, United Kingdom [email protected] 2 University of Kent, Canterbury, United Kingdom fm.paviotti, sjc205, daw29, S.A.Owens, [email protected] 3 ETH Zurich, Switzerland [email protected] Abstract. We present a denotational semantics for weak memory con- currency that avoids thin-air reads, provides data-race free programs with sequentially consistent semantics (DRF-SC), and supports a com- positional refinement relation for validating optimisations. Our semantics identifies false program dependencies that might be removed by compiler optimisation, and leaves in place just the dependencies necessary to rule out thin-air reads. We show that our dependency calculation can be used to rule out thin-air reads in any axiomatic concurrency model, in particular C++. We present a tool that automatically evaluates litmus tests, show that we can augment C++ to fix the thin-air problem, and we prove that our augmentation is compatible with the previously used compilation mappings over key processor architectures. We argue that our dependency calculation offers a practical route to fixing the long- standing problem of thin-air reads in the C++ specification. Keywords: Thin-air problem · Weak memory concurrency · Compiler Optimisations · Denotational Semantics · Compositionality 1 Introduction It has been a longstanding problem to define the semantics of programming languages with shared memory concurrency in a way that does not allow un- wanted behaviours { especially observing thin-air values [8,7] { and that does not forbid compiler optimisations that are important in practice, as is the case with Java and Hotspot [30,29]. -
Concurrency Semantics in Continuation-Passing Style — The
Concurrency Semantics in Continuation-Passing Style∗ — The Companion Technical Report — Eneia Nicolae Todoran Technical University of Cluj-Napoca Department of Computer Science Baritiu Str. 28, 400027, Cluj-Napoca, Romania. [email protected] Nikolaos S. Papaspyrou National Technical University of Athens School of Electrical and Computer Engineering Software Engineering Laboratory Polytechnioupoli, 15780 Zografou, Greece. [email protected] Abstract By using the mathematical framework of metric semantics we develop a denotational semantics designed in continuation-passing style for an abstract concurrent language providing a general mech- anism of interaction between multisets of distributed actions. The basic laws of concurrent systems are satisfied in this semantics. Next, by customizing the behavior of continuations we obtain denota- tional semantics for a couple of concurrent languages incorporating mechanisms for multiparty and binary interactions. We offer denotational semantics for two imperative concurrent languages based on Hoare’s CSP and a process algebra for DNA computing introduced by Cardelli. Keywords: continuation-passing style, denotational semantics, metric spaces, concurrency semantics 1 Introduction Continuations are a very powerful control-flow mechanism. As abstract representations of control flow, they were introduced in the 1960s and soon came into prominence in the field of denotational semantics for modelling the semantics of programming languages [23, 38, 34]. In a few words, a continuation represents control flow by capturing the notion of “the rest of the program”, after the current point during the program’s execution. Some functional languages, such as Scheme [22] and SML/NJ [37], provide direct support for capturing and invoking continuations, which are treated as first-class values.