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GIT—a heuristic program for testing pairs of directed line graphs for isomorphism
Given a pair of directed line graphs, the problem of ascertaining whether or not they are isomorphic is one for which no efficient algorithmic solution is known. Since a straightforward enumerative algorithm might require 40 years of running time on a very high speed computer in order to compare two 15-node graphs, a more sophisticated approach seems called for. The situation is similar to that prevailing in areas such as game-playing and theorem-proving, where practical algorithms are unknown (for the interesting cases), but where various practical though only partially successful techniques are available. GIT—Graph Isomorphism Tester—incorporates a variety of processes that attempt to narrow down the search for an isomorphism, or to demonstrate that none exists. No one scheme is relied upon exclusively for a solution, and the program is designed to avoid excessive computation along fruitless lines. GIT has been written in the COMIT language and successfully tested on the IBM 7090.
Floating-point arithmetic with 84-bit numbers
A classic and straightforward technique is presented which is not limited to the size or type of number representation used or multiple precision arithmetic.
A fast procedure for generating normal random variables
A technique for generating normally distributed random numbers is described. It is faster than those currently in general use and is readily applicable to both binary and decimal computers.
Use of the disk file on stretch
The paper begins by briefly describing the Stretch (IBM 7030) computer with special emphasis given to the organization and operation of its input-output equipment. Physical characteristics of the two-disk system (4,194,304 72-bit words, 8 µsec-per-word transmission rate, etc.) are noted. Timing limitations due to arm motion and disk rotation are discussed.
Applications of disk usage are discussed separately for problem programs and for systems programs such as compilers and the supervisory program. Approximately 260,000 words of disk storage are reserved for the storage of systems programs and the subroutine library. Problem programs, however, are not currently filed on the disk.
Certain programming techniques are discussed for transmitting words between disk and core storage with minimum delaying and interruption of the arithmetic unit. Dumps on disk are considered for both recovery from computer malfunction and for mathematical or physical developments during the calculation.
Computation’s development critical to our society
The ACM's growth continues: we are now at 13,000 members; expenses also grow. Our professional membership does not spring from a uniformly trained group as in mathematics or physics or even economics. Instead, our increasing membership comes from what I might call intellectual adventures—pioneers in an over-organized society—who see great futures in computing at all levels of aspiration.
A comparison of disks and tapes
The principal characteristics of current magnetic disks and tape units are summarized and compared. Some of the characteristics of disk files are illustrated in a sorting example and compared to a tapesort. The conclusion is presented that disk files are competitive to tapes in some important applications.
DATA-DIAL: two-way communication with computers from ordinary dial telphones
An operating system is described which allows users to call up a remotely located computer from ordinary dial telephones. No special hardware or connections are required at the users' telephones. Input to the computer is through the telephone dial; output from the computer is in spoken form. Results of a test with telephones in the Boston area are reported.
An experiment in automatic verification of programs
How effective is a compiler at replacing explicit verification, and what is the cost of this technique?
Character addressable, variable field computers permit ready establishment and manipulation of variable width stacks. Single machine commands may push variable field items down into such stacks or pop them up. The availability of a variety of field delimiters allows the machine to push down or pop up more than one variable width item with one command. Since these stacking operations can be made the basis of compiler decoding algorithms, the proper use of machines of this class for compilation has advantages over machines with fixed-length words.
Soviet cybernetics and computer sciences, 1960
This article records observations on Soviet research and technology in cybernetics and computer science, made by the author during a visit to the Soviet Union as a delegate to the IFAC Congress on Automatic Control held in Moscow in the summer of 1960.
What is proprietary in mathematical programming?— impressions of a panel discussion
A panel discussion on “What is Proprietary in Mathematical Programming?” was sponsored by the Special Interest Committee on Mathematical Programming of the ACM during a Hall of Discussion/on September 7th at the 16TH National ACM meeting in Los Angeles. This note consists solely of the impressions garnered by the moderator of the panel and does not necessarily represent the position of any of the panelists or other participants in the discussion.
n-dimensional codes for detecting and correcting multiple errors0
The paper introduces a new family of codes for detecting and correcting multiple errors in a binary-coded message. The message itself is arranged (conceptually) into a multidimensional rectangular array. The processes of encoding and error detection are based upon parity evaluations along prescribed dimensions of the array. Effectiveness of the codes is increased by introducing a “system check bit”, which is essentially a parity check on the other parity bits. Only three-dimensional codes are discussed in this paper, with parity evaluations along the horizontal, the vertical, and one main diagonal. However, the family of codes is not restricted to three dimensions, as evidenced by the discussion by Minnick and Ashenhurst on a similar multidimensional single-bit selection plan used for another purpose [6]. A four-dimensional code, correcting three and detecting four errors, has been developed; the extension to higher-dimensional codes with greater correction power is straightforward.
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