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Communications of the ACM

Table of Contents


ACM president's letter: fireside chat


Improving the access time for random access files

Clustering in the key set is decreased by smoothing the key-to-address transformation, and by adding shadow buckets to an open chaining file. The keys are pre-hashed before the address division, to remove the effect of sequential …

Effective information retrieval using term accuracy

The performance of information retrieval systems can be evaluated in a number of different ways. Much of the published evaluation work is based on measuring the retrieval performance of an average user query. Unfortunately, formal …

Empirical evaluation of some features of instruction set processor architectures

This paper presents methods for empirical evaluation of features of Instruction Set Processors (ISPs). ISP features are evaluated in terms of the time used or saved by having or not having the feature. The methods are based on …

Memory management and response time

This paper presents a computationally tractable methodology for including accurately the effects of finite memory size and workload memory requirements in queueing network models of computer systems. Empirical analyses and analytic …

Representation of many-sided polygons and polygonal lines for rapid processing

A representation for polygons and polygonal lines is described which allows sets of consecutive sides to be collectively examined. The set of sides are arranged in a binary tree hierarchy by inclusion. A fast algorithm for testing …

Operations on sparse relations

Various computations on relations, Boolean matrices, or directed graphs, such as the computation of precedence relations for a context-free grammar, can be done by a practical algorithm that is asymptotically faster than those …

Effects of chargeout on user/manager attitutes

The relationship of internal pricing systems for computer services (chargeout systems) and user management attitudes about their computer-based information systems is investigated. Evidence is provided that the relationship conforms …

Cost/utilization: a measure of system performance

A method is presented for evaluating computer system performance in terms of a cost/utilization factor and a measure of imbalance. These coefficients indicate the extent to which the total system cost is effectively utilized. …

A comparison of next-fit, first-fit, and best-fit

“Next-fit” allocation differs from first-fit in that a first-fit allocator commences its search for free space at a fixed end of memory, whereas a next-fit allocator commences its search wherever it previously stopped searching …

The storage requirement in precedence parsing


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