Introductory principles of program performance in virtual storage have been presented to give a perspective of the virtual environment for systems designers and programmers. It is recognized that the list of guideline...
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Introductory principles of program performance in virtual storage have been presented to give a perspective of the virtual environment for systems designers and programmers. It is recognized that the list of guidelines presented is not comprehensive as many more useful techniques will be developed as experience is gained with virtual storage systems. It is hoped that these program design considerations and the programming guidelines will assist these users in their future virtual storage program development.
A classic problem in security is that of checking that a program has secure information flow. informally, this problem is described as follows: Given a program with variables partitioned into mio disjoint sets of &quo...
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A classic problem in security is that of checking that a program has secure information flow. informally, this problem is described as follows: Given a program with variables partitioned into mio disjoint sets of "high-security" and "low-security" variables, check whether observations of the low-security variables reveal any information about the initial values of the high-security variables. Although the problem has been studied for serveral decades, most previous approaches have been syntactic in nature, often using type systems and compiler data flow analysis techniques to analyze program texts. This paper presents a considerably different approach to check secure information flow, based on a semantic characterization. A semantic approach has several desirable features. Firstly, it gives a more precise characterization of security than that provided by most previous approaches. Secondly, it applies to any programming constructs whose semantics are definable;for instance, the introduction of nondeterminism and exceptions poses no additional problems. Thirdly, it can be used for reasoning about indirect leaking of information through variations in program behavior (e.g., whether or not the program terminates). Finally, it can be extended to the case where the high- and low-security variables are defined abstractly, as functions of actual program variables. The paper illustrates the use of the characterization with several examples and discusses how it can be applied in practice. (C) 2000 Elsevier Science B.V. All rights reserved.
This paper presents program analyses and transformations for strengthening invariants for the purpose of efficient computation. Finding the stronger invariants corresponds to discovering a general class of auxiliary i...
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This paper presents program analyses and transformations for strengthening invariants for the purpose of efficient computation. Finding the stronger invariants corresponds to discovering a general class of auxiliary information for any incremental computation problem. Combining the techniques with previous techniques for caching intermediate results, we obtain a systematic approach that transforms non-incremental programs into efficient incremental programs that use and maintain useful auxiliary information as well as useful intermediate results. The use of auxiliary information allows us to achieve a greater degree of incrementality than otherwise possible. Applications of the approach include strength reduction in optimizing compilers and finite differencing in transformational programming. (C) 2001 Elsevier Science B.V. All rights reserved.
Functional simulation of direct-access storage devices allows for testing and experimenting with a current or new direct-access device without it being available or attached to the system. In particular, the MVE mode ...
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Functional simulation of direct-access storage devices allows for testing and experimenting with a current or new direct-access device without it being available or attached to the system. In particular, the MVE mode of DSIM allows the simulation of devices under any operating system. The techniques provided are data-driven, thus allowing the simulation of devices with differing characteristics. T he interactive options enable the user to create or check for errors and thus provide for testing of the various error routines associated with the device. This capability is not generally attainable even with the real device. By extending the measurement routines, other device performance statistics may also be obtained. DSIM does not impair the security of the data within the system on which it is being used since it will not access any existing data within the system. DSIM is useful as an experimental intervirtual machine communication mechanism.
This paper discusses the relationship between machine organization and control program design in high-end commercial computersystems. The criterion is cost/performance, subject to achieving an acceptable performance ...
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This paper discusses the relationship between machine organization and control program design in high-end commercial computersystems. The criterion is cost/performance, subject to achieving an acceptable performance level. A brief discussion of the environment expected for the design and operation of high-end commercial computersystems is outlined, followed by a discussion of machine organization techniques which are classified and reviewed to permit a qualitative evaluation of the degree to which control program intent is exploited in machine organization. The thesis is developed next, using a hierarchical model which illustrates the contention that architecture has acted as a barrier to communication between the control program and machine organization. Examples of techniques that exploit knowledge of the intent of the control program and comments on the methodology that might be used to investigate such techniques follow. Directions for further research are then proposed.
The Interpretive Frame System (IFS) is a tool for creating application software with sophisticated interactive interfaces. IFS is based on the notion of a frame network. A frame network consists of many interconnected...
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The Interpretive Frame System (IFS) is a tool for creating application software with sophisticated interactive interfaces. IFS is based on the notion of a frame network. A frame network consists of many interconnected modules called frames, each of which represents a logical activity in the system. Frames are written in a high-level language. Besides the usual computational constructs such as conditionals, loops, or arithmetics and Boolean expressions, the IFS language also includes facilities for building program/program interactions, such as subprocess invocations or coprocess communications, and constructs for building user/program interactions such as menus or forms. IFS is a suitable tool to integrate existing programs by providing a uniform and easy-to-use user interface. It can also be used to build a new system in a top-down manner by first defining the network of frames and their interactions and user interface, then programming problem-specific parts. Therefore, it provides a general framework supporting any combination of top-down and bottom-up software development methodologies. This paper gives an overview of the frame network concept, the user interface of frame network systems, the frame programming language, and the IFS system implementation.
We examine the functional capabilities of a symbolic execution subsystem for programs written in MIXAL assembly language and consider the procedure for selection of test data from the results of symbolic execution. Sy...
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We examine the functional capabilities of a symbolic execution subsystem for programs written in MIXAL assembly language and consider the procedure for selection of test data from the results of symbolic execution. Symbolic execution of a program involves its interpretation of symbolic input data. This symbolic execution subsystem is a component of a mutlipurpose integrated program development system in a assembly-type language implemented on ES computers.
A central challenge in computer science and knowledge representation is the integration of conceptual frameworks for continuous and discrete change, as exemplified by the theory of differential equations and real anal...
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A central challenge in computer science and knowledge representation is the integration of conceptual frameworks for continuous and discrete change, as exemplified by the theory of differential equations and real analysis on the one hand, and the theory of programming languages on the other. We take the first steps towards such an integrated. theory by presenting a recipe for the construction of continuous programming languages - languages in which state dynamics can be described by differential equations. The basic idea is to start with an untimed language and extend it uniformly over dense (real) time. We present a concrete mathematical model and language (the Hybrid concurrent constraint programming model, Hybrid cc) instantiating these ideas. The language is intended to be used for modeling and programming hybrid systems. The language is declarative - programs can be understood as formulas that place constraints on the (temporal) evolution of the system, with parallel composition regarded as conjunction. It is expressive - it allows the definition of continuous versions of the preemption control constructs. The language is obtained by extending the general-purpose computational formalism of (default) concurrent constraint programming (Default cc) with a single temporal construct, called hence - hence A is read as asserting that A holds continuously beyond the current instant. Various patterns of temporal activity can be generated from this single construct by use of the other combinators in Default cc. We provide a precise operational semantics according to which execution alternates between (i) points at which discontinuous change can occur, and (ii) open intervals in which the state of the system changes continuously. Transitions from a state of continuous evolution are triggered when some condition starts or stops holding. We show that the denotational semantics is correct for reasoning about the operational semantics, through an adequacy theorem. (C) 1998 El
Two versions of the parallel bucket sorting algorithm ensuring nearly optimal speedup on SIMD computers are considered. The algorithm is divided into two stages. In the first stage, the array elements are assigned to ...
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Two versions of the parallel bucket sorting algorithm ensuring nearly optimal speedup on SIMD computers are considered. The algorithm is divided into two stages. In the first stage, the array elements are assigned to buckets, and in the second stage the contents of all the buckets are sorted concurrently.
Task partitioning is an important technique in parallel *** this paper,we investigate the optimal partitioning strategies and granularities of tasks with communications based on several models of parallel computer ***...
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Task partitioning is an important technique in parallel *** this paper,we investigate the optimal partitioning strategies and granularities of tasks with communications based on several models of parallel computer *** from the usual approach,we study the optimal partitioning strate- gies and granularities from the viewpoint of minimizing T as well as minimizing NT^2,where N is the number of processors used and T is the program execution time using N *** results show that the optimal partitioning strategies for all cases discussed in this paper are the same——either to as- sign all tasks to one processor or to distribute them among the processors as equally as possible de- pending only on the functions of ratio of running time to communication time R/C.
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