Reactive programming and event-based programming are two closely related programming styles that are becoming ever more important with the advent of advanced HCI technology and the ever increasing requirement for appl...
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ISBN:
(纸本)9781450337229
Reactive programming and event-based programming are two closely related programming styles that are becoming ever more important with the advent of advanced HCI technology and the ever increasing requirement for applications to run on the web or on collaborating mobile devices. A number of publications about middleware and languagedesign - so-called reactive and event-based languages and systems - have already seen the light, but the field still raises several questions. For example, the interaction with mainstream language concepts is poorly understood, implementation technology is in its infancy and modularity mechanisms are almost totally lacking. Moreover, large applications are still to be developed and patterns and tools for developing reactive applications is an area that is vastly unexplored. This workshop gathers researchers in reactive and event-based languages and systems. The goal of the workshop is to exchange new technical research results and to define better the field by coming up with taxonomies and overviews of the existing work.
Performance and energy efficiency in memory have become critically important for a wide range of computing domains. However, it is difficult to control and optimize memory power and performance because these effects d...
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ISBN:
(纸本)9781450336895
Performance and energy efficiency in memory have become critically important for a wide range of computing domains. However, it is difficult to control and optimize memory power and performance because these effects depend upon activity across multiple layers of the vertical execution stack. To address this challenge, we construct a novel and collaborative framework that employs object placement, cross-layer communication, and page-level management to effectively distribute application objects in the DRAM hardware to achieve desired power/performance goals. In this work, we describe the design and implementation of our framework, which is the first to integrate automatic object profiling and analysis at the application layer with fine-grained management of memory hardware resources in the operating system. We demonstrate the utility of our framework by employing it to more effectively control memory power consumption. We design a custom memory-intensive workload to show the potential of our approach. Next, we develop sampling and profiling-based analyses and modify the code generator in the HotSpot VM to understand object usage patterns and automatically determine and control the placement of hot and cold objects in a partitioned VM heap. This information is communicated to the operating system, which uses it to map the logical application pages to the appropriate DRAM ranks according to user-defined provisioning goals. We evaluate our framework and find that it achieves our test goal of significant DRAM energy savings across a variety of workloads, without any source code modifications or recompilations.
We propose a new memory-safe interpretation of the C abstract machine that provides stronger protection to benefit security and debugging. Despite ambiguities in the specification intended to provide implementation fl...
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ISBN:
(纸本)9781450328357
We propose a new memory-safe interpretation of the C abstract machine that provides stronger protection to benefit security and debugging. Despite ambiguities in the specification intended to provide implementation flexibility, contemporary implementations of C have converged on a memory model similar to the PDP-11, the original target for C. This model lacks support for memory safety despite well-documented impacts on security and reliability. Attempts to change this model are often hampered by assumptions embedded in a large body of existing C code, dating back to the memory model exposed by the original C compiler for the PDP-11. Our experience with attempting to implement a memory-safe variant of C on the CHERI experimental microprocessor led us to identify a number of problematic idioms. We describe these as well as their interaction with existing memory safety schemes and the assumptions that they make beyond the requirements of the C specification. Finally, we refine the CHERI ISA and abstract model for C, by combining elements of the CHERI capability model and fat pointers, and present a softcore CPU that implements a C abstract machine that can run legacy C code with strong memory protection guarantees.
Many verifications of realistic software systems are monolithic, in the sense that they define single global invariants over complete system state. More modular proof techniques promise to support reuse of component p...
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This paper describes a general framework-and its implementation in a tool called EXPLORER-for statically answering a class of interprocedural control flow queries about Java programs. EXPLORER allows users to formulat...
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This paper describes a general framework-and its implementation in a tool called EXPLORER-for statically answering a class of interprocedural control flow queries about Java programs. EXPLORER allows users to formulate queries about feasible callstack configurations using regular expressions, and it employs a precise, demand-driven algorithm for answering such queries. Specifically, EXPLORER constructs an automaton A that is iteratively refined until either the language accepted by A is empty (meaning that the query has been refuted) or until no further refinement is possible based on a precise, context-sensitive abstraction of the program. We evaluate EXPLORER by applying it to three different program analysis tasks, namely, (1) analysis of the observer design pattern in Java, (2) identification of a class of performance bugs, and (3) analysis of inter-component communication in Android applications. Our evaluation shows that EXPLORER is both efficient and precise.
We present a way to restrict recursive inheritance without sacrificing the benefits of F-bounded polymorphism. In particular, we distinguish two new concepts, materials and shapes, and demonstrate through a survey of ...
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ISBN:
(纸本)9781450327848
We present a way to restrict recursive inheritance without sacrificing the benefits of F-bounded polymorphism. In particular, we distinguish two new concepts, materials and shapes, and demonstrate through a survey of 13.5 million lines of open-source generic-Java code that these two concepts never actually overlap in practice. With this Material-Shape Separation, we prove that even naive type-checking algorithms are sound and complete, some of which address problems that were unsolvable even under the existing proposals for restricting inheritance. We illustrate how the simplicity of our design reflects the design intuitions employed by programmers and potentially enables new features coming into demand for upcoming programminglanguages.
Syntactic sugar is pervasive in language technology. It is used to shrink the size of a core language;to define domain-specific languages;and even to let programmers extend their language. Unfortunately, syntactic sug...
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ISBN:
(纸本)9781450327848
Syntactic sugar is pervasive in language technology. It is used to shrink the size of a core language;to define domain-specific languages;and even to let programmers extend their language. Unfortunately, syntactic sugar is eliminated by transformation, so the resulting programs become unfamiliar to authors. Thus, it comes at a price: it obscures the relationship between the user's source program and the program being evaluated. We address this problem by showing how to compute reduction steps in terms of the surface syntax. Each step in the surface language emulates one or more steps in the core language. The computed steps hide the transformation, thus maintaining the abstraction provided by the surface language. We make these statements about emulation and abstraction precise, prove that they hold in our formalism, and verify part of the system in Coq. We have implemented this work and applied it to three very different languages.
We address the problem of synthesizing code completions for programs using APIs. Given a program with holes, we synthesize completions for holes with the most likely sequences of method calls. Our main idea is to redu...
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ISBN:
(纸本)9781450327848
We address the problem of synthesizing code completions for programs using APIs. Given a program with holes, we synthesize completions for holes with the most likely sequences of method calls. Our main idea is to reduce the problem of code completion to a natural-language processing problem of predicting probabilities of sentences. We design a simple and scalable static analysis that extracts sequences of method calls from a large codebase, and index these into a statistical language model. We then employ the language model to find the highest ranked sentences, and use them to synthesize a code completion. Our approach is able to synthesize sequences of calls across multiple objects together with their arguments. Experiments show that our approach is fast and effective. Virtually all computed completions typecheck, and the desired completion appears in the top 3 results in 90% of the cases.
Tree automata and tree transducers are used in a wide range of applications in software engineering, from XML processing to language type-checking. While these formalisms are of immense practical use, they can only mo...
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ISBN:
(纸本)9781450327848
Tree automata and tree transducers are used in a wide range of applications in software engineering, from XML processing to language type-checking. While these formalisms are of immense practical use, they can only model finite alphabets, and since many real-world applications operate over in finite domains such as integers, this is often a limitation. To overcome this problem we augment tree automata and transducers with symbolic alphabets represented as parametric theories. Admitting in finite alphabets makes these models more general and succinct than their classical counterparts. Despite this, we show how the main operations, such as composition and language equivalence, remain computable given a decision procedure for the alphabet theory. We introduce a high-level language called Fast that acts as a front-end for the above formalisms. Fast supports symbolic alphabets through tight integration with state-of-the art satisfiability modulo theory (SMT) solvers. We demonstrate our techniques on practical case studies, covering a wide range of applications.
Determinism is an appealing property for parallel programs, as it simplifies understanding, reasoning and debugging. It is particularly appealing in dynamic (scripting) languages, where ease of programming is a domina...
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ISBN:
(纸本)9781450327848
Determinism is an appealing property for parallel programs, as it simplifies understanding, reasoning and debugging. It is particularly appealing in dynamic (scripting) languages, where ease of programming is a dominant design goal. Some existing parallel languages use the type system to enforce determinism statically, but this is not generally practical for dynamic languages. In this paper, we describe how determinism can be obtained-and dynamically enforced/verified-for appropriate extensions to a parallel scripting language. Specifically, we introduce the constructs of Deterministic Parallel Ruby (DPR), together with a run-time system (TARDIS) that verifies properties required for determinism, including correct usage of reductions and commutative operators, and the mutual independence (data-race freedom) of concurrent tasks. Experimental results confirm that DPR can provide scalable performance on multicore machines and that the overhead of TARDIS is low enough for practical testing. In particular, TARDIS significantly outperforms alternative data-race detectors with comparable functionality. We conclude with a discussion of future directions in the dynamic enforcement of determinism.
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