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Communications of the ACM

Table of Contents


Systems design education: a gaming approach

One of the problems facing managers of computer installations is the problem of configuring the computer system to meet the demands made by the mix of jobs that the computer center must service, This paper presents a management …

A simply extended and modified batch environment graphical system (SEMBEGS)

SEMBEGS is a complete batch environment graphical system containing components for handling graphical data files, for displaying the contents of these files on a variety of graphical hardware, and for performing graphical batch …

Performance evaluation of highly concurrent computers by deterministic simulation

Simulation is presented as a practical technique for performance evaluation of alternative configurations of highly concurrent computers. A technique is described for constructing a detailed deterministic simulation model of  …

Using synthetic images to register real images with surface models

A number of image analysis tasks can benefit from registration of the image with a model of the surface being imaged. Automatic navigation using visible light or radar images requires exact alignment of such images with digital …

Computer generation of gamma random variables—II

A rejection method is proposed for generating gamma variates with nonintegral shape parameter &agr;, &agr; > 1. This method is similar to other methods given by Fishman, Wallace, and Tadikamalla and is faster than these methods for&agr;&agr; …

A simple recovery-only procedure for simple precedence parsers

A simple method is described enabling simple precedence parsers to recover from syntax errors. No attempt to repair errors is made, yet parsing and most semantic processing can continue. The result is a good “first approximation” …

A note on conditional expressions

Evaluation of a conditional expression may succeed even when the “deciding predicate” diverges and the alternatives are records (or nodes) whose fields have different content.

Distributed processes: a concurrent programming concept

A language concept for concurrent processes without common variables is introduced. These processes communicate and synchronize by means of procedure calls and guarded regions. This concept is proposed for real-time applications …

Power trees

The new class of Pk trees is presented, where height balance is maintained for the nodes lying on particular paths. The number of nodes of a Pk tree asympotically grows as a power of the height, in the worst case. A procedure …

Median split trees: a fast lookup technique for frequently occuring keys

Split trees are a new technique for searching sets of keys with highly skewed frequency distributions. A split tree is a binary search tree each node of which contains two key values—a node value which is a maximally frequent …

Synthesizing constraint expressions

A constraint network representation is presented for a combinatorial search problem: finding values for a set of variables subject to a set of constraints. A theory of consistency levels in such networks is formulated, which  …

On-the-fly garbage collection: an exercise in cooperation

As an example of cooperation between sequential processes with very little mutual interference despite frequent manipulations of a large shared data space, a technique is developed which allows nearly all of the activity needed …

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