20,868 research outputs found

    Pervasive Parallel And Distributed Computing In A Liberal Arts College Curriculum

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    We present a model for incorporating parallel and distributed computing (PDC) throughout an undergraduate CS curriculum. Our curriculum is designed to introduce students early to parallel and distributed computing topics and to expose students to these topics repeatedly in the context of a wide variety of CS courses. The key to our approach is the development of a required intermediate-level course that serves as a introduction to computer systems and parallel computing. It serves as a requirement for every CS major and minor and is a prerequisite to upper-level courses that expand on parallel and distributed computing topics in different contexts. With the addition of this new course, we are able to easily make room in upper-level courses to add and expand parallel and distributed computing topics. The goal of our curricular design is to ensure that every graduating CS major has exposure to parallel and distributed computing, with both a breadth and depth of coverage. Our curriculum is particularly designed for the constraints of a small liberal arts college, however, much of its ideas and its design are applicable to any undergraduate CS curriculum

    Clarifying and compiling C/C++ concurrency: from C++11 to POWER

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    The upcoming C and C++ revised standards add concurrency to the languages, for the first time, in the form of a subtle *relaxed memory model* (the *C++11 model*). This aims to permit compiler optimisation and to accommodate the differing relaxed-memory behaviours of mainstream multiprocessors, combining simple semantics for most code with high-performance *low-level atomics* for concurrency libraries. In this paper, we first establish two simpler but provably equivalent models for C++11, one for the full language and another for the subset without consume operations. Subsetting further to the fragment without low-level atomics, we identify a subtlety arising from atomic initialisation and prove that, under an additional condition, the model is equivalent to sequential consistency for race-free programs

    Bridging the Gap between Programming Languages and Hardware Weak Memory Models

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    We develop a new intermediate weak memory model, IMM, as a way of modularizing the proofs of correctness of compilation from concurrent programming languages with weak memory consistency semantics to mainstream multi-core architectures, such as POWER and ARM. We use IMM to prove the correctness of compilation from the promising semantics of Kang et al. to POWER (thereby correcting and improving their result) and ARMv7, as well as to the recently revised ARMv8 model. Our results are mechanized in Coq, and to the best of our knowledge, these are the first machine-verified compilation correctness results for models that are weaker than x86-TSO

    Scaling Bounded Model Checking By Transforming Programs With Arrays

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    Bounded Model Checking is one the most successful techniques for finding bugs in program. However, model checkers are resource hungry and are often unable to verify programs with loops iterating over large arrays.We present a transformation that enables bounded model checkers to verify a certain class of array properties. Our technique transforms an array-manipulating (ANSI-C) program to an array-free and loop-free (ANSI-C) program thereby reducing the resource requirements of a model checker significantly. Model checking of the transformed program using an off-the-shelf bounded model checker simulates the loop iterations efficiently. Thus, our transformed program is a sound abstraction of the original program and is also precise in a large number of cases - we formally characterize the class of programs for which it is guaranteed to be precise. We demonstrate the applicability and usefulness of our technique on both industry code as well as academic benchmarks

    C์˜ ์ €์ˆ˜์ค€ ๊ธฐ๋Šฅ๊ณผ ์ปดํŒŒ์ผ๋Ÿฌ ์ตœ์ ํ™” ์กฐํ™”์‹œํ‚ค๊ธฐ

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ๊ณต๊ณผ๋Œ€ํ•™ ์ปดํ“จํ„ฐ๊ณตํ•™๋ถ€, 2019. 2. ํ—ˆ์ถฉ๊ธธ.์ฃผ๋ฅ˜ C ์ปดํŒŒ์ผ๋Ÿฌ๋“ค์€ ํ”„๋กœ๊ทธ๋žจ์˜ ์„ฑ๋Šฅ์„ ๋†’์ด๊ธฐ ์œ„ํ•ด ๊ณต๊ฒฉ์ ์ธ ์ตœ์ ํ™”๋ฅผ ์ˆ˜ํ–‰ํ•˜๋Š”๋ฐ, ๊ทธ๋Ÿฐ ์ตœ์ ํ™”๋Š” ์ €์ˆ˜์ค€ ๊ธฐ๋Šฅ์„ ์‚ฌ์šฉํ•˜๋Š” ํ”„๋กœ๊ทธ๋žจ์˜ ํ–‰๋™์„ ๋ฐ”๊พธ๊ธฐ๋„ ํ•œ๋‹ค. ๋ถˆํ–‰ํžˆ๋„ C ์–ธ์–ด๋ฅผ ๋””์ž์ธํ•  ๋•Œ ์ €์ˆ˜์ค€ ๊ธฐ๋Šฅ๊ณผ ์ปดํŒŒ์ผ๋Ÿฌ ์ตœ์ ํ™”๋ฅผ ์ ์ ˆํ•˜๊ฒŒ ์กฐํ™”์‹œํ‚ค๊ฐ€ ๊ต‰์žฅํžˆ ์–ด๋ ต๋‹ค๋Š” ๊ฒƒ์ด ํ•™๊ณ„์™€ ์—…๊ณ„์˜ ์ค‘๋ก ์ด๋‹ค. ์ €์ˆ˜์ค€ ๊ธฐ๋Šฅ์„ ์œ„ํ•ด์„œ๋Š”, ๊ทธ๋Ÿฌํ•œ ๊ธฐ๋Šฅ์ด ์‹œ์Šคํ…œ ํ”„๋กœ๊ทธ๋ž˜๋ฐ์— ์‚ฌ์šฉ๋˜๋Š” ํŒจํ„ด์„ ์ž˜ ์ง€์›ํ•ด์•ผ ํ•œ๋‹ค. ์ปดํŒŒ์ผ๋Ÿฌ ์ตœ์ ํ™”๋ฅผ ์œ„ํ•ด์„œ๋Š”, ์ฃผ๋ฅ˜ ์ปดํŒŒ์ผ๋Ÿฌ๊ฐ€ ์ˆ˜ํ–‰ํ•˜๋Š” ๋ณต์žกํ•˜๊ณ ๋„ ํšจ๊ณผ์ ์ธ ์ตœ์ ํ™”๋ฅผ ์ž˜ ์ง€์›ํ•ด์•ผ ํ•œ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ์ €์ˆ˜์ค€ ๊ธฐ๋Šฅ๊ณผ ์ปดํŒŒ์ผ๋Ÿฌ ์ตœ์ ํ™”๋ฅผ ๋™์‹œ์— ์ž˜ ์ง€์›ํ•˜๋Š” ์‹คํ–‰์˜๋ฏธ๋Š” ์˜ค๋Š˜๋‚ ๊นŒ์ง€ ์ œ์•ˆ๋œ ๋ฐ”๊ฐ€ ์—†๋‹ค. ๋ณธ ๋ฐ•์‚ฌํ•™์œ„ ๋…ผ๋ฌธ์€ ์‹œ์Šคํ…œ ํ”„๋กœ๊ทธ๋ž˜๋ฐ์—์„œ ์š”๊ธดํ•˜๊ฒŒ ์‚ฌ์šฉ๋˜๋Š” ์ €์ˆ˜์ค€ ๊ธฐ๋Šฅ๊ณผ ์ฃผ์š”ํ•œ ์ปดํŒŒ์ผ๋Ÿฌ ์ตœ์ ํ™”๋ฅผ ์กฐํ™”์‹œํ‚จ๋‹ค. ๊ตฌ์ฒด์ ์œผ๋กœ, ์šฐ๋ฆฐ ๋‹ค์Œ ์„ฑ์งˆ์„ ๋งŒ์กฑํ•˜๋Š” ๋Š์Šจํ•œ ๋™์‹œ์„ฑ, ๋ถ„ํ•  ์ปดํŒŒ์ผ, ์ •์ˆ˜-ํฌ์ธํ„ฐ ๋ณ€ํ™˜์˜ ์‹คํ–‰์˜๋ฏธ๋ฅผ ์ฒ˜์Œ์œผ๋กœ ์ œ์•ˆํ•œ๋‹ค. ์ฒซ์งธ, ๊ธฐ๋Šฅ์ด ์‹œ์Šคํ…œ ํ”„๋กœ๊ทธ๋ž˜๋ฐ์—์„œ ์‚ฌ์šฉ๋˜๋Š” ํŒจํ„ด๊ณผ, ๊ทธ๋Ÿฌํ•œ ํŒจํ„ด์„ ๋…ผ์ฆํ•  ์ˆ˜ ์žˆ๋Š” ๊ธฐ๋ฒ•์„ ์ง€์›ํ•œ๋‹ค. ๋‘˜์งธ, ์ฃผ์š”ํ•œ ์ปดํŒŒ์ผ๋Ÿฌ ์ตœ์ ํ™”๋“ค์„ ์ง€์›ํ•œ๋‹ค. ์šฐ๋ฆฌ๊ฐ€ ์ œ์•ˆํ•œ ์‹คํ–‰์˜๋ฏธ์— ์ž์‹ ๊ฐ์„ ์–ป๊ธฐ ์œ„ํ•ด ์šฐ๋ฆฌ๋Š” ๋…ผ๋ฌธ์˜ ์ฃผ์š” ๊ฒฐ๊ณผ๋ฅผ ๋Œ€๋ถ€๋ถ„ Coq ์ฆ๋ช…๊ธฐ ์œ„์—์„œ ์ฆ๋ช…ํ•˜๊ณ , ๊ทธ ์ฆ๋ช…์„ ๊ธฐ๊ณ„์ ์ด๊ณ  ์—„๋ฐ€ํ•˜๊ฒŒ ํ™•์ธํ–ˆ๋‹ค.To improve the performance of C programs, mainstream compilers perform aggressive optimizations that may change the behaviors of programs that use low-level features in unidiomatic ways. Unfortunately, despite many years of research and industrial efforts, it has proven very difficult to adequately balance the conflicting criteria for low-level features and compiler optimizations in the design of the C programming language. On the one hand, C should support the common usage patterns of the low-level features in systems programming. On the other hand, C should also support the sophisticated and yet effective optimizations performed by mainstream compilers. None of the existing proposals for C semantics, however, sufficiently support low-level features and compiler optimizations at the same time. In this dissertation, we resolve the conflict between some of the low-level features crucially used in systems programming and major compiler optimizations. Specifically, we develop the first formal semantics of relaxed-memory concurrency, separate compilation, and cast between integers and pointers that (1) supports their common usage patterns and reasoning principles for programmers, and (2) provably validates major compiler optimizations at the same time. To establish confidence in our formal semantics, we have formalized most of our key results in the Coq theorem prover, which automatically and rigorously checks the validity of the results.Abstract Acknowledgements Chapter I Prologue Chapter II Relaxed-Memory Concurrency Chapter III Separate Compilation and Linking Chapter IV Cast between Integers and Pointers Chapter V Epilogue ์ดˆ๋กDocto

    Diagnosis and Repair for Synthesis from Signal Temporal Logic Specifications

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    We address the problem of diagnosing and repairing specifications for hybrid systems formalized in signal temporal logic (STL). Our focus is on the setting of automatic synthesis of controllers in a model predictive control (MPC) framework. We build on recent approaches that reduce the controller synthesis problem to solving one or more mixed integer linear programs (MILPs), where infeasibility of a MILP usually indicates unrealizability of the controller synthesis problem. Given an infeasible STL synthesis problem, we present algorithms that provide feedback on the reasons for unrealizability, and suggestions for making it realizable. Our algorithms are sound and complete, i.e., they provide a correct diagnosis, and always terminate with a non-trivial specification that is feasible using the chosen synthesis method, when such a solution exists. We demonstrate the effectiveness of our approach on the synthesis of controllers for various cyber-physical systems, including an autonomous driving application and an aircraft electric power system

    Chaotic Crystallography: How the physics of information reveals structural order in materials

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    We review recent progress in applying information- and computation-theoretic measures to describe material structure that transcends previous methods based on exact geometric symmetries. We discuss the necessary theoretical background for this new toolset and show how the new techniques detect and describe novel material properties. We discuss how the approach relates to well known crystallographic practice and examine how it provides novel interpretations of familiar structures. Throughout, we concentrate on disordered materials that, while important, have received less attention both theoretically and experimentally than those with either periodic or aperiodic order.Comment: 9 pages, two figures, 1 table; http://csc.ucdavis.edu/~cmg/compmech/pubs/ChemOpinion.ht

    A gradient system with a wiggly energy and relaxed EDP-convergence

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    If gradient systems depend on a microstructure, we want to derive a macroscopic gradient structure describing the effective behavior of the microscopic effects. We introduce a notion of evolutionary Gamma-convergence that relates the microscopic energy and the microscopic dissipation potential with their macroscopic limits via Gamma-convergence. This new notion generalizes the concept of EDP-convergence, which was introduced in arXiv:1507.06322, and is called "relaxed EDP-convergence". Both notions are based on De Giorgi's energy-dissipation principle, however the special structure of the dissipation functional in terms of the primal and dual dissipation potential is, in general, not preserved under Gamma-convergence. By investigating the kinetic relation directly and using general forcings we still derive a unique macroscopic dissipation potential. The wiggly-energy model of James et al serves as a prototypical example where this nontrivial limit passage can be fully analyzed.Comment: 43 pages, 8 figure
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