Proceedings 1976 Summer Computer Simulation Conference

BOOK REVIEWS Proceedings 1976 Summer Computer Simulation Conference AFIPS Press, Montvale, N.J., USA, 1976. 1040 pp. The conference dealt with nearly 200 papers spaced over eleven groups which ranged from methodology through specific disciplines including environmental and social science to simulation credibility. In criticism it should be noted that two papers were almost identical, in the sense that they had substantially the same diagrams and identical introductory text. This is acceptable if two distinct applications are chosen but both these papers dealt with pneumatic tyre modelling. The reviewer was particularly struck by the way the Fortran-orientated languages are finding the need for structured programming constructs. Two papers-‘a simulator for material handling systems’ and ‘a system for the automatic evaluation of system softwave’-found it necessary to implement such instructions as do while and if’. then else. This is quite significant as far as simulation language development is concerned. At the other end of the scale, the reviewer is still unable to see any virtue in using analog computers for essentially digital tasks such as the factorization of a polynomial into quadratic factors. The technique, incidentally is very similar to that used to solve linear equations on an analog computer-an equally dubious pursuit. There was a reasonable presentation which dealt with ‘an interactive version of GASP IV for minicomputers’, using a 16K store and a DOS. This should be read in conjunction with the paper dealing with recent developments of DARE for DEC 28K computers. Two papers of note were, in order, ‘modelling events which take a finite time to occur’-by avoiding the proliferation of change states which should prove to be readily adaptable to the logic design fields where the rise and fall times can interact disastrously. The other was ‘A high performance logic simulator’ specifically designed to check for races and hazards. Although a paper on the use of power series to implement the integration of ordinary differential equations made interesting reading, it must be borne in mind that the preliminary mathematical processing might prove to be a little off-putting. In view of the present interest in microprocessors a paper on ‘A semaphor synchronised multiprocessor

with central control’ which uses a hierarchy of processes, executed in parallel, should prove of interest to many computer engineers. A paper on ‘Program reliability and testing by means of simulation’ was a little general but worthy of attention as were ‘Dynamic testing of simulation softwave’ and ‘Validation tests for softwave error simulation models’ which used a graph theory implementation. In an allied field. a ‘Database evaluation simulation model was quite interesting. but unfortunately no results were published. In the field of parameter optimization and identification there were again two papers of particular interest. One showed that good convergence results from a ‘sequential regression method of parameter identification’ for both dynamic and non-dynamic systems in which both the input and output were corrupted by noise. The other on ‘Parameter estimation for system dynamics models’ with both corrupted and missing data compared the results advantageously to those of the ordinary least squares estimates. Finally. two papers which caught the eye as being ‘interest’ papers. In the first, the matching of a fishing fleet to the factory on shore in the light of a quota system tied in well with the current interest in conservation. In the second. simulation was used as an aid to the analysis of the operational problems of a police department using GASP II and Q-GERTS. This produced the tit-bit that if New York City can borrow $9 000 000 at 13% the savings would repay the loan in IO years. 6. Girting

Systems analysis, planning and decision models W. K. M. Brauers Elsevier, Amsterdam, The Netherlands, 1976. US $21.25 Systems Analysis is defined by the author as ‘inquiry to assist decision makers in choosing preferred future courses of action.. .’ Thus this is not a book about the analysis of computer systems. It is a well-structured and easily readable book. ‘It is the result of research into the building of overall defence planning and decision models. As such it is not a text that could be recommended as an introduction to the techniques of operational analysis but it is a valuable addition to the literature

Appl.

Math.

for those involved at a high academic level in planning and decision modelling. The author’s claim, that the approach adopted in the book is equally applicable to organisations in the public and private sector in addition to defence is valid, and in general, the book covers well the material that it claims to. In conclusion this is a well-produced book and would be a good book to have on one’s library shelf although the price might be a bit off putting.

J. S. Wild

Mathematical linear systems W. J. Rugh Marcel Dekker, 177 pp. $13.50

description

New

of

York, 1975.

This book gives a brief, introductory account of the theory of linear control systems using state-space methods. Chapter 1 presents some simple models together with material on the solution of linear systems. Chapter 2 covers reachability and observability, Chapter 3 develops the use of z and Idaplace transforms for transfer function representation, Chapter 4 deals with realization and Chapter 5 discusses stability including the Routh (misnamed RouthhHurwitz) and Jury criteria. There is also a chapter containing less standard material on identification. and a final chapter briefly treats time delay systems, sampled data systems and linearization. There are some nice features about this book, especially the way the models of chapter 1 are used as illustrative examples throughout the text. and the simultaneous development of discretetime and continuous-time theory. It is unfortunate that only single-input singleoutput systems are considered. Much of the power and generality of the statespace approach is thus left unappreciated. However, bearing in mind this limitation the book is quite useful as a readable, relatively informal treatment of basic topics. For a deeper account Desoer’s ‘Notes for a second course on linear systems’ (Van Nostrand Reinhold, 1970) is to be preferred. The book is acceptably reproduced from typescript but even by present standards its price is rather high. Stephen

Modelling,

1977,

Barnett

Vol. 1, June

285