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Communications of the ACM

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A letter from the ACM vice-president: concerns of our members —a report from an ACM forum


A comparative study of computer programs for integrating differential equations

A study comparing the performance of several computer programs for integrating systems of ordinary differential equations is reported. The integration methods represented include multistep methods (predictor-correctors), single …

Algorithms to reveal properties of floating-point arithmetic

Two algorithms are presented in the form of Fortran subroutines. Each subroutine computes the radix and number of digits of the floating-point numbers and whether rounding or chopping is done by the machine on which it is run …

A highly parallel algorithm for approximating all zeros of a polynomial with only real zeros

An algorithm is described based on Newton's method which simultaneously approximates all zeros of a polynomial with only real zeros. The algorithm, which is conceptually suitable for parallel computation, determines its own starting …

A model for type checking: with an application to ALGOL 60

Most current programming languages treat computation over different classes of objects (e.g. numbers, strings, labels and functions). For correct compilation and execution, the following question then arises: is a program properly …

Derived semantics for some programming language constructs

The constructs of a simple programming language are introduced and described informally in terms of values and side-effects. A translator is defined which translates the language into flowcharts for a simple machine. The action …

The conversion of limited-entry decision tables to optimal and near-optimal flowcharts: two new algorithms

Two new algorithms for deriving optimal and near-optimal flowcharts from limited entry decision tables are presented. Both take into account rule frequencies and the time needed to test conditions. One of the algorithms, called …

Garbage collection for virtual memory computer systems

In list processing there is typically a growing demand for space during program execution. This paper examines the practical implications of this growth within a virtual memory computer system, proposes two new garbage collection …

An approximate method for generating symmetric random variables

A method for generating values of continuous symmetric random variables that is relatively fast, requires essentially no computer memory, and is easy to use is developed. The method, which uses a uniform zero-one random number …

Algorithm 434: exact probabilities for R×C contingency tables [G2]


Exact probabilities for R x C contingency tables [G2]


Algorithm 435: modified incomplete gamma function [S14]


Algorithm 434: modified incomplete gamma function [G 2]


Additional results on key-to-address transform techniques: a fundamental performance study on large existing formatted files

In an earlier paper by Lum, Yuen, and Dodd [1] experimental results comparing six commonly used key-to-address transformation techniques were presented. One transformation in that study referred to as “Lin's method” is an elaborate …

A note on optimal doubly-chained trees

This note concerns the recent paper by Hu [2] dealing with doubly-chained trees of the type introduced by Sussenguth [9]. In the second part of the paper, Hu deals with the problem of constructing an optimum weighted doubly-chained …

Further comments on Dijkstra's concurrent programming control problem

E.W. Dijkstra [1] presented an algorithm whereby N mainly independent computers, with a common data store as their sole means of communication, could contend for exclusive control of any given resource (storage, I/O, etc.). To …

Comments on Moorer's music and computer composition

J.A. Moorer's “Music and Computer Composition” [1] was a distressing communication. While I realize that musical expertise is probably beyond the realm of the editorial staff, I must object to both the naiveté and faulty reasoning …

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