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Communications of the ACM

Table of Contents


ACM president's letter: about the refereeing process


Matrix reduction—an efficient method

The paper describes an efficient method for reduction of the binary matrices which arise in some school time-tabling problems. It is a development of that described by John Lions. It has been generalized and adapted to fit into …

A system for typesetting mathematics

This paper describes the design and implementation of a system for typesetting mathematics. The language has been designed to be easy to learn and to use by people (for example, secretaries and mathematical typists) who know …

Glypnir—a programming language for Illiac IV

GLYPNIR is one of the earliest existing languages designed for programming the Illiac IV computer. The syntax of the language is based on ALGOL 60, but has been extended to allow the programmer explicitly to specify the parallelism …

Expected time bounds for selection

A new selection algorithm is presented which is shown to be very efficient on the average, both theoretically and practically. The number of comparisons used to select the ith smallest of n numbers is n + min(i,n-i) + o(n). A …

Algorithm 489: the algorithm SELECT—for finding the ith smallest of n elements [M1]

SELECT will rearrange the values of array segment X[L: R] so that X[K] (for some given K; LKR) will contain the (K-L+1)-th smallest value, LIK will imply X[I] ≤ X[K], and KIR will imply X[I] ≥ X[K. While SELECT …

A reply to gentleman and Marovich

Gentleman and Marovich in their short communication [Comm. ACM 17, 5 (May 1974) 276-277] make the claim that for FORTRAN “… the language definitions require that subprograms can be separately compiled…,” citing the ANSI FORTRAN …

The algorithm sequential access method: an alternative to index sequential

A requirement of many computer file processing systems is the ability to access data stored on a direct access storage device (DASD) both sequentially and randomly. A popular method which provides both types of access is the  …

On computing certain elements of the inverse of a sparse matrix

A recursive algorithm for computing the inverse of a matrix from the LU factors based on relationships in Takahashi, et al., is examined. The formulas for the algorithm are given; the dependency relationships are derived; the …

Discrete least squares polynomial fits

The recurrence relation between orthogonal polynomials is widely used for discrete least squares data fitting. A variant of the classical algorithm which has better numerical properties is presented and the reason for its improved …

On a solution to the cigarette smoker's problem (without conditional statements)

This report discusses a problem first introduced by Patil, who has claimed that the cigarette smoker's problem cannot be solved using the P and V operations introduced by Dijkstra unless conditional statements are used. An examination …

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