A transient hardware fault occurs when an energetic particle strikes a transistor, causing it to change state. Although transient faults do not permanently damage the hardware, they may corrupt computations by alterin...
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ISBN:
(纸本)9781595936332
A transient hardware fault occurs when an energetic particle strikes a transistor, causing it to change state. Although transient faults do not permanently damage the hardware, they may corrupt computations by altering stored values and signal transfers. In this paper, we propose a new scheme for provably safe and reliable computing in the presence of transient hardware faults. In our scheme, software computations are replicated to provide redundancy while special instructions compare the independently computed results to detect errors before writing critical data. In stark contrast to any previous efforts in this area, we have analyzed our fault tolerance scheme from a formal, theoretical perspective. To be specific, first, we provide an operational semantics for our assembly language, which includes a precise formal definition of our fault model. Second, we develop an assembly-level type system designed to detect reliability problems in compiled code. Third, we provide a formal specification for program fault tolerance under the given fault model and prove that all well-typed programs are indeed fault tolerant. In addition to the formal analysis, we evaluate our detection scheme and show that it only takes 34% longer to execute than the unreliable version.
Operators for delimiting control and for capturing composable continuations litter the landscape of theoretical programminglanguage research. Numerous papers explain their advantages, how the operators explain each o...
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ISBN:
(纸本)9781595938152
Operators for delimiting control and for capturing composable continuations litter the landscape of theoretical programminglanguage research. Numerous papers explain their advantages, how the operators explain each other (or don't), and other aspects of the operators' existence. Production programminglanguages, however, do not support these operators, partly because their relationship to existing and demonstrably useful constructs-such as exceptions and dynamic binding-remains relatively unexplored. In this paper, we report on our effort of translating the theory of delimited and composable control into a viable implementation for a production system. The report shows how this effort involved a substantial design element, including work with a formal model, as well as significant practical exploration and engineering. The resulting version of PLT Scheme incorporates the expressive combination of delimited and composable control alongside dynamic-wind, dynamic binding, and exception handling. None of the additional operators subvert the intended benefits of existing control operators, so that programmers can freely mix and match control operators.
Transactional memory provides a new concurrency control mechanism that avoids many of the pitfalls of lock-based synchronization. High-performance software transactional memory (STM) implementations thus far provide w...
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ISBN:
(纸本)9781595936332
Transactional memory provides a new concurrency control mechanism that avoids many of the pitfalls of lock-based synchronization. High-performance software transactional memory (STM) implementations thus far provide weak atomicity: Accessing shared data both inside and outside a transaction can result in unexpected, implementation-dependent behavior. To guarantee isolation and consistent ordering in such a system, programmers are expected to enclose all shared-memory accesses inside transactions. A system that provides strong atomicity guarantees isolation even in the presence of threads that access shared data outside transactions. A strongly-atomic system also orders transactions with conflicting non-transactional memory operations in a consistent manner. In this paper, we discuss some surprising pitfalls of weak atomicity, and we present an STM system that avoids these problems via strong atomicity. We demonstrate how to implement non-transactional data accesses via efficient read and write barriers, and we present compiler optimizations that further reduce the overheads of these barriers. We introduce a dynamic escape analysis that differentiates private and public data at runtime to make barriers cheaper and a static not-accessed-in-transaction analysis that removes many barriers completely. Our results on a set of Java programs show that strong atomicity can be implemented efficiently in a high-performance STM system.
This paper tells the story of the development of BETA: a programminglanguage with just one abstraction mechanism, instead of one abstraction mechanism for each kind of program element (classes, types, procedures, fun...
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The JastAdd Extensible Java Compiler is a high quality Java compiler that is easy to extend in order to build static analysis tools for Java, and to extend Java with new language constructs. It is built modularly, wit...
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ISBN:
(纸本)9781595937865
The JastAdd Extensible Java Compiler is a high quality Java compiler that is easy to extend in order to build static analysis tools for Java, and to extend Java with new language constructs. It is built modularly, with a Java 1.4 compiler that is extended to a Java 5 compiler. Example applications that are built as extensions include an alternative backend that generates Jimple, an extension of Java with AspectJ constructs, and the implementation of a pluggable type system for non-null checking and inference. The system is implemented using JastAdd, a declarative Java-like language. We describe the compiler architecture, the major design ideas for building and extending the compiler, in particular, for dealing with complex extensions that affect name and type analysis. Our extensible compiler compares very favorably concerning quality, speed and size with other extensible Java compiler frameworks. It also compares favorably in quality and size compared with traditional non-extensible Java compilers, and it runs within a factor of three compared to javac.
Existing languages provide good support for typeful programming of stand-alone programs. In a distributed system, however, there may be interaction between multiple instances of many distinct programs, sharing some (b...
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ISBN:
(纸本)9781595930644
Existing languages provide good support for typeful programming of stand-alone programs. In a distributed system, however, there may be interaction between multiple instances of many distinct programs, sharing some (but not necessarily all) of their module structure, and with some instances rebuilt with new versions of certain modules as time goes on. In this paper, we discuss programming-language support for such systems, focussing on their typing and naming issues. We describe an experimental language, Acute, which extends an ML core to support distributed development, deployment, and execution, allowing type-safe interaction between separately built programs. The main features are (1) type-safe marshalling of arbitrary values;(2) type names that are generated (freshly and by hashing) to ensure that type equality tests suffice to protect the invariants of abstract types, across the entire distributed system;(3) expression-level names generated to ensure that name equality tests suffice for type safety of associated values, for example, values carried on named channels;(4) controlled dynamic rebinding of marshalled values to local resources;and (5) thunkification of threads and mutexes to support computation mobility. These features are a large part of what is needed for typeful distributed programming. They are a relatively lightweight extension of ML, should be efficiently implementable, and are expressive enough to enable a wide variety of distributed infrastructure layers to be written as simple library code above the byte-string network and persistent store APIs. This disentangles the language run-time from communication intricacies. This paper highlights the main design choices in Acute. It is supported by a full language definition (of typing, compilation, and operational semantics), by a prototype implementation, and by example distribution libraries.
The years 1985 through 1995 saw the birth and development of the language Self, starting from its design by the authors at Xerox PARC, through first implementations by Ungar and his graduate students at Stanford Unive...
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ML modules and Haskell type classes have proven to be highly effective tools for program structuring. Modules emphasize explicit configuration of program components and the use of data abstraction. Type classes emphas...
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ISBN:
(纸本)9781595935755
ML modules and Haskell type classes have proven to be highly effective tools for program structuring. Modules emphasize explicit configuration of program components and the use of data abstraction. Type classes emphasize implicit program construction and ad hoc polymorphism. In this paper, we show how the implicitly-typed style of type class programming may be supported within the framework of an explicitly-typed module language by viewing type classes as a particular mode of use of modules. This view offers a harmonious integration of modules and type classes, where type class features, such as class hierarchies and associated types, arise naturally as uses of existing module-language constructs, such as module hierarchies and type components. In addition, programmers have explicit control over which type class instances are available for use by type inference in a given scope. We formalize our approach as a Harper-Stone-style elaboration relation, and provide a sound type inference algorithm as a guide to implementation.
In this paper we introduce the iTask system: a set of combinators to specify work flows in a pure functional language at a very high level of abstraction. Work flow systems are automated systems in which tasks are coo...
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ISBN:
(纸本)9781595938152
In this paper we introduce the iTask system: a set of combinators to specify work flows in a pure functional language at a very high level of abstraction. Work flow systems are automated systems in which tasks are coordinated that have to be executed by humans and computers. The combinators that we propose support work flow patterns commonly found in commercial work flow systems. Compared with most of these commercial systems, the iTask system offers several advantages: tasks are statically typed, tasks can be higher order, the combinators are fully compositional, dynamic and recursive work flows can be specified, and last but not least, the specification is used to generate an executable web-based multi-user work flow application. With the iTask system, useful work flows can be defined which cannot be expressed in other systems: work can be interrupted and subsequently directed to other workers for further processing. The implementation is special as well. It is based on the Clean iData toolkit which makes it possible to create fully dynamic, interactive, thin client web applications. Thanks to the generic programming techniques used in the iData toolkit, the programming effort is reduced significantly: state handling, form rendering, user interaction, and storage management is handled automatically. The iTask system allows a task to be regarded as a special kind of persistent redex being reduced by the application user via task completion. The combinators control the order in which these redexes are made available to the application user. The system rewrites the persistent task redexes in a similar way as functions are rewritten in lazy functional languages.
Future mainstream microprocessors will likely integrate specialized accelerators, such as GPUs, onto a single die to achieve better performance and power efficiency. However, it remains a keen challenge to program suc...
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ISBN:
(纸本)9781595936332
Future mainstream microprocessors will likely integrate specialized accelerators, such as GPUs, onto a single die to achieve better performance and power efficiency. However, it remains a keen challenge to program such a heterogeneous multi-core platform, since these specialized accelerators feature ISAs and functionality that are significantly different from the general purpose CPU cores. In this paper. we present EXOCHI: (1) Exoskeleton Sequencer (EXO), an architecture to represent heterogeneous accelerators as ISA-based MIMD architecture resources, and a shared virtual memory heterogeneous multithreaded program execution model that tightly couples specialized accelerator cores with general purpose CPU cores, and (2) C for Heterogeneous Integration (CHI), an integrated C/C++ programming environment that supports accelerator-specific inline assembly and domain-specific languages. The CHI compiler extends the OpenMP pragma for heterogeneous multithreading programming, and produces a single fat binary with code sections corresponding to different instruction sets. The runtime can judiciously spread parallel Computation across the heterogenous cores to optimize performance and power. We have prototyped the EXO architecture on a physical heterogeneous platform consisting of an Intel (R) Core (TM) 2 Duo Processor and an 8-core 32-thread Intel (R) Graphics Media Accelerator X3000. In addition. we have implemented the CHI integrated programming environment with the Intel (R) C++ Compiler, runtime toolset. and debugger. On the EXO prototype system, we have enhanced a suite of production-quality media kernels for video and image processing to utilize the accelerator through the CHI programming interface, achieving significant speedup (1.41x to 10.97x) over execution on the IA32 CPU alone.
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