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The Bedrock Structured programming System Combining Generative Metaprogramming and Hoare Logic in an Extensible Program Verifier

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acm sigplan NOTICES 2013年第9期48卷 391-402页

作者： Chlipala, Adam MIT CSAIL United States

We report on the design and implementation of an extensible programming language and its intrinsic support for formal verification. Our language is targeted at low-level programming of infrastructure like operating systems and runtime systems. It is based on a cross-platform core combining characteristics of assembly languages and compiler intermediate languages. From this foundation, we take literally the saying that C is a "macro assembly language": we introduce an expressive notion of certified low-level macros, sufficient to build up the usual features of C and beyond as macros with no special support in the core. Furthermore, our macros have integrated support for strongest postcondition calculation and verification condition generation, so that we can provide a high-productivity formal verification environment within Coq for programs composed from any combination of macros. Our macro interface is expressive enough to support features that low-level programs usually only access through external tools with no formal guarantees, such as declarative parsing or SQL-inspired querying. The abstraction level of these macros only imposes a compile-time cost, via the execution of functional Coq programs that compute programs in our intermediate language;but the run-time cost is not substantially greater than for more conventional C code. We describe our experiences constructing a full C-like language stack using macros, with some experiments on the verifiability and performance of individual programs running on that stack.

关键词： generative metaprogramming interactive proof assistants low-level programming languages functional programming

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TRANSIT: Specifying Protocols with Concolic Snippets 13

TRANSIT: Specifying Protocols with Concolic Snippets

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acm sigplan conference on programming language design and implementation

作者： Abhishek Udupa Sela Mador-Haim Arun Raghavan Milo M. K. Martin Jyotirmoy V. Deshmukh Rajeev Alur University of Pennsylvania Toyota Technical Center

ISBN: (纸本)9781450320146

With the maturing of technology for model checking and constraint solving, there is an emerging opportunity to develop programming tools that can transform the way systems are specified. In this paper, we propose a new way to program distributed protocols using concolic snippets. Concolic snippets are sample execution fragments that contain both concrete and symbolic values. The proposed approach allows the programmer to describe the desired system partially using the traditional model of communicating extended finite-state-machines (EFSM), along with high-level invariants and concrete execution fragments. Our synthesis engine completes an EFSM skeleton by inferring guards and updates from the given fragments which is then automatically analyzed using a model checker with respect to the desired invariants. The counterexamples produced by the model checker can then be used by the programmer to add new concrete execution fragments that describe the correct behavior in the specific scenario corresponding to the counterexample. We describe TRANSIT, a language and prototype implementation of the proposed specification methodology for distributed protocols. Experimental evaluations of TRANSIT to specify cache coherence protocols show that (1) the algorithm for expression inference from concolic snippets can synthesize expressions of size 15 involving typical operators over commonly occurring types, (2) for a classical directory-based protocol, TRANSIT automatically generates, in a few seconds, a complete implementation from a specification consisting of the EFSM structure and a few concrete examples for every transition, and (3) a published partial description of the SGI Origin cache coherence protocol maps directly to symbolic examples and leads to a complete implementation in a few iterations, with the programmer correcting counterexamples resulting from underspecified transitions by adding concrete examples in each iteration.

关键词： Program Synthesis Distributed Protocol Synthesis Cache Coherence Protocols programming by Example

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General Data Structure Expansion for Multi-threading 13

General Data Structure Expansion for Multi-threading

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acm sigplan conference on programming language design and implementation

作者： Hongtao Yu Hou-Jen Ko Zhiyuan Li Department of Computer Science Purdue University

ISBN: (纸本)9781450320146

Among techniques for parallelizing sequential codes, privatization is a common and significant transformation performed by both compilers and runtime parallelizing systems. Without privatization, repetitive updates to the same data structures often introduce spurious data dependencies that hide the inherent parallelism. Unfortunately, it remains a significant challenge to compilers to automatically privatize dynamic and recursive data structures which appear frequently in real applications written in languages such as C/C++. This is because such languages lack a naming mechanism to define the address range of a pointer-based data structure, in contrast to arrays with explicitly declared bounds. In this paper we present a novel solution to this difficult problem by expanding general data structures such that memory accesses issued from different threads to contentious data structures are directed to different data fields. Based on compile-time type checking and a data dependence graph, this aggressive extension to the traditional scalar and array expansion isolates the address ranges among different threads, without struggling with privatization based on thread-private stacks, such that the targeted loop can be effectively parallelized. With this method fully implemented in GCC, experiments are conducted on a set of programs from well-known benchmark suites such as Mibench, MediaBench II and SPECint. Results show that the new approach can lead to a high speedup when executing the transformed code on multiple cores.

关键词： Parallelization Privatization Multithreading Algorithms languages Performance Privatisation Multithreading Data structures language parallelization data dependency compilers algorithms type checking

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Session details: language design 13

Session details: Language design

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Proceedings of the 34th acm sigplan conference on programming language design and implementation

作者： Umut A. Acar Carnegie Mellon University

No abstract available.

ISBN: (纸本)9781450320146

No abstract available.

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programming languages in security: keynote 13

Programming languages in security: keynote

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Proceedings of the 34th acm sigplan conference on programming language design and implementation

作者： Fred B. Schneider Cornell University Ithaca NY USA

No abstract available.

ISBN: (纸本)9781450320146

No abstract available.

关键词： science of security

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Fast RMWs for TSO: Semantics and implementation 13

Fast RMWs for TSO: Semantics and Implementation

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acm sigplan conference on programming language design and implementation

作者： Bharghava Rajaram Vijay Nagarajan Susmit Sarkar Marco Elver University of Edinburgh University of St Andrews

ISBN: (纸本)9781450320146

Read-Modify-Write (RMW) instructions are widely used as the building blocks of a variety of higher level synchronization constructs, including locks, barriers, and lock-free data structures. Unfortunately, they are expensive in architectures such as x86 and SPARC which enforce (variants of) Total-Store-Order (TSO). A key reason is that RMWs in these architectures are ordered like a memory barrier, incurring the cost of a write-buffer drain in the critical path. Such strong ordering semantics are dictated by the requirements of the strict atomicity definition (type-1) that existing TSO RMWs use. Programmers often do not need such strong semantics. Besides, weakening the atomicity definition of TSO RMWs, would also weaken their ordering - thereby leading to more efficient hardware implementations. In this paper we argue for TSO RMWs to use weaker atomicity definitions - we consider two weaker definitions: type-2 and type-3, with different relaxed ordering differences. We formally specify how such weaker RMWs would be ordered, and show that type-2 RMWs, in particular, can seamlessly replace existing type-1 RMWs in common synchronization idioms - except in situations where a type-1 RMW is used as a memory barrier. Recent work has shown that the new C/C++11 concurrency model can be realized by generating conventional (type-1) RMWs for C/C++11 SC-atomic-writes and/or SC-atomic-reads. We formally prove that this is equally valid using the proposed type-2 RMWs; type-3 RMWs, on the other hand, could be used for SC-atomic-reads (and optionally SC-atomic-writes). We further propose efficient microarchitectural implementations for type-2 (type-3) RMWs - simulation results show that our implementation reduces the cost of an RMW by up to 58.9% (64.3%), which translates into an overall performance improvement of up to 9.0% (9.2%) on a set of parallel programs, including those from the SPLASH-2, PARSEC, and STAMP benchmarks.

关键词： Read-Modify-Write (RMW) Total-Store-Order (TSO) Atomics design Performance Experimentation

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CLAP: Recording Local Executions to Reproduce Concurrency Failures 13

CLAP: Recording Local Executions to Reproduce Concurrency Fa...

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acm sigplan conference on programming language design and implementation

作者： Jeff Huang Charles Zhang Julian Dolby Hong Kong University of Science and Technology IBM Thomas J. Watson Research Center

ISBN: (纸本)9781450320146

We present CLAP, a new technique to reproduce concurrency bugs. CLAP has two key steps. First, it logs thread local execution paths at runtime. Second, offline, it computes memory dependencies that accord with the logged execution and are able to reproduce the observed bug. The second step works by combining constraints from the thread paths and constraints based on a memory model, and computing an execution with a constraint solver. CLAP has four major advantages. First, logging purely local execution of each thread is substantially cheaper than logging memory interactions, which enables CLAP to be efficient compared to previous approaches. Second, our logging does not require any synchronization and hence with no added memory barriers or fences; this minimizes perturbation and missed bugs due to extra synchronizations foreclosing certain racy behaviors. Third, since it uses no synchronization, we extend CLAP to work on a range of relaxed memory models, such as TSO and PSO, in addition to sequential consistency. Fourth, CLAP can compute a much simpler execution than the original one, that reveals the bug with minimal thread context switches. To mitigate the scalability issues, we also present an approach to parallelize constraint solving, which theoretically scales our technique to programs with arbitrary execution length. Experimental results on a variety of multithreaded benchmarks and real world concurrent applications validate these advantages by showing that our technique is effective in reproducing concurrency bugs even under relaxed memory models; furthermore, it is significantly more efficient than a state-of-the-art technique that records shared memory dependencies, reducing execution time overhead by 45% and log size by 88% on average.

关键词： Concurrency Bug Reproduction Local Execution Constraint Solving Algorithms design Performance Theory

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Isolation for Nested Task Parallelism

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acm sigplan NOTICES 2013年第10期48卷 571-587页

作者： Zhao, Jisheng Lublinerman, Roberto Budimlic, Zoran Chaudhuri, Swarat Sarkar, Vivek Rice Univ Houston TX 77251 USA Google Inc Mountain View CA USA

Isolation-the property that a task can access shared data without interference from other tasks-is one of the most basic concerns in parallel programming. While there is a large body of past work on isolated task-parallelism, the integration of isolation, task-parallelism, and nesting of tasks has been a difficult and unresolved challenge. In this paper, we present a programming and execution model called Otello where isolation is extended to arbitrarily nested parallel tasks with irregular accesses to heap data. At the same time, no additional burden is imposed on the programmer, who only exposes parallelism by creating and synchronizing parallel tasks, leaving the job of ensuring isolation to the underlying compiler and runtime system. Otello extends our past work on Aida execution model and the delegated isolation mechanism [22] to the setting of nested parallelism. The basic runtime construct in Aida and Otello is an assembly: a task equipped with a region in the shared heap that it owns. When an assembly A conflicts with an assembly B, A transfers-or delegates-its code and owned region to a carefully selected assembly C in a way that will ensure isolation with B, leaving the responsibility of re-executing task A to C. The choice of C depends on the nesting relationship between A and B. We have implemented Otello on top of the Habanero Java (HJ) parallel programming language [8], and used this implementation to evaluate Otello on collections of nested task-parallel benchmarks and non-nested transactional benchmarks from past work. On the nested task-parallel bench-marks, Otello achieves scalability comparable to HJ programs without built-in isolation, and the relative overhead of Otello is lower than that of many published data-race detection algorithms that detect the isolation violations (but do not enforce isolation). For the transactional benchmarks, Otello incurs lower overhead than a state-of-the-art software transactional memory system (Deuce STM).

关键词： languages design Isolation programming abstractions Irregular parallelism Contention

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Reagents: Expressing and Composing Fine-grained Concurrency 12

Reagents: Expressing and Composing Fine-grained Concurrency

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33rd acm sigplan conference on programming language design and implementation

作者： Turon, Aaron Northeastern Univ Boston MA 02115 USA

ISBN: (纸本)9781450312059

Efficient communication and synchronization is crucial for fine-grained parallelism. Libraries providing such features, while indispensable, are difficult to write, and often cannot be tailored or composed to meet the needs of specific users. We introduce reagents, a set of combinators for concisely expressing concurrency algorithms. Reagents scale as well as their hand-coded counterparts, while providing the composability existing libraries lack.

关键词： design Algorithms languages Performance fine-grained concurrency nonblocking algorithms monads arrows compositional concurrency

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Compiling a high-level language for GPUs: Via language support for architectures and compilers

Compiling a high-level language for GPUs: Via language suppo...

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33rd acm sigplan conference on programming language design and implementation, pldi'12

作者： Dubach, Christophe Cheng, Perry Rabbah, Rodric Bacon, David F. Fink, Stephen J. University of Edinburgh United Kingdom IBM Research United States

ISBN: (纸本)9781450312059

languages such as OpenCL and CUDA offer a standard interface for general-purpose programming of GPUs. However, with these languages, programmers must explicitly manage numerous lowlevel details involving communication and synchronization. This burden makes programming GPUs difficult and error-prone, rendering these powerful devices inaccessible to most programmers. We desire a higher-level programming model that makes GPUs more accessible while also effectively exploiting their computational power. This paper presents features of Lime, a new Javacompatible language targeting heterogeneous systems, that allow an optimizing compiler to generate high quality GPU code. The key insight is that the language type system enforces isolation and immutability invariants that allow the compiler to optimize for a GPU without heroic compiler analysis. Our compiler attains GPU speedups between 75% and 140% of the performance of native OpenCL code. Copyright © 2012 acm.

关键词： Lime

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