Nash - Scientific Computing with PCs (523165), страница 2
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Dobb’s JournalTrademarksThe following table lists, as far as we could determine, the holders of various trademarks mentioned inthis work.Trademark HolderAdobe Systems Inc.American Mathematical SocietyApple Computer CorporationAptech Systems Inc.Borland International, Inc.C Ware CorporationConceptual Software Inc.Corel CorporationCrescent Software Inc.Data Description Inc.Data Viz IncGazelle SystemsGibson Research Inc.Hewlett-PackardIntel CorporationInternational Business Machines Inc.Lotus Development Corp.The MathWorks Inc.Microsoft CorporationMinitab Inc.MotorolaNash Information Services Inc.NeXT Computer Inc.Numerical Algorithms Group Inc.Scientific Endeavors Corp.Stata CorporationSun Microsystems, Inc.Soft Warehouse Inc.Strategy Plus Inc.Stac Electronics Inc.SYSTAT Inc.
(now part of SPSS Inc.)Travelling Software Inc.True BASIC Inc.UNIX System Laboratories Inc.Waterloo Maple SoftwareWolfram ResearchWordPerfect CorporationZilog CorporationTrademark(s) or Trade Name(s)PostScriptTEXApple, MacintoshGAUSSBRIEF, dBase III, dBase IV, PARADOX, Turbo Basic, TurboPascal, Turbo C, Borland C, Turbo C++, Borland C++, Quattro,Quattro ProSEE, DeSmet C, DeSmet ASM88DBMSCOPYCorelDRAW, CorelPHOTO-PAINTGraphPakData DeskMacLinkOPTuneSpinRiteHewlett-PackardIntel, 386IBM, RS6000, OS/2Lotus, 1-2-3MATLABExcel, Microsoft, Quick C, MS-DOS, Windows, Quick BASIC,Visual BASICMINITABMotorola, 6800, 68000SnoopGuardNeXTNAGGraphiCStataSUNDERIVE, muMATHEXECUSTATSTACKERSYSTAT, MYSTATLaplinkTrue BASICUNIXMapleMathematicaWordPerfectZ80Previous1: INTRODUCTION AND PURPOSEHome1Part I: PanoramaTo get a good idea of the lie of the land, one finds a convenient tree, hill or building andexploits the larger field of view gained by height.
As a preliminary to the detailed studyof the application of personal computers (PCs) to scientific computation, we will takesuch a panoramic view. First, a chapter on the aims (and non-aims) of this book, whichconcern the way in which scientific problems are solved and the role of computationsin such solutions.Chapter 1Introduction and Purpose:How Scientific Problems are Solved1.11.21.31.41.5BackgroundGoalsThe scientific method and our audienceComputer configurations of interestComputing stylesThis book aims to help researchers who are not computer specialists to use PCs profitably and efficiently.It is especially concerned with the strategies and tactics that enable users to carry out their scientific workin all aspects — technical, administrative and educational — with the aid of PCs.
We do not claim thatPCs are the "best" answer for scientific computations but point out that they deserve consideration. Indeedour message is that there is no uniquely "best" approach to scientific problem solving, but that there aregenerally several options that will provide satisfactory results with modest expenditure of time andmoney.
It is toward reasoned consideration of the PC option that we direct our energies here.1.1BackgroundThe PCs of this book are primarily those of the IBM PC family, with the Apple Macintosh also kept inmind. We will use the abbreviation PC to refer to machines of both the IBM PC (that is, MS-DOS) familyand the Apple Macintosh.
Because we have less familiarity with Atari and Commodore machines, thereare few references to them. Workstations based on the UNIX operating system, such as SUN, NeXT, IBMRS6000, certain Hewlett-Packard machines and many others, have not been used as examples, mainlybecause our use of such machines has been limited. The ideas presented in this book can nevertheless beapplied to such machines, particularly if the reader is the system manager. The software and manner ofuse of workstations is, in our opinion, qualitatively different from that of PCs and Macintoshes in that theworkstations are less independent machines than parts of larger networks.
While many PCs are alsoconnected in networks, the type of central support provided is more likely, we think, to be limited toNext2Copyright © 1984, 1994 J C & M M NashNash Information Services Inc., 1975 Bel Air Drive, Ottawa, ON K2C 0X1 CanadaSCIENTIFIC COMPUTING WITH PCsCopy for:Dr. Dobb’s Journalnon-scientific applications. Thus there is a qualitative difference between the PC world and the (UNIX)workstation world in the technical support provided to the user for scientific computations.We note that both IBM PC and Macintosh can be operated under variants of Unix, and that OS/2 isanother choice of operating system for IBM PC users.
As we write, Microsoft is introducing Windows NT.We will mention such environments as appropriate, but they are not critical to our examples.The realities of present-day PCs are as interesting as the publicity that surrounds them. However, thereis a lot less glamour to be found in the reality of PCs than in the advertising copy. This introductionpresents the authors’ goals in writing this book, suggests the type of reader who will find it most useful,and declares several topics that will not be covered.We will caution that advertised products need to be evaluated carefully.
New products may be able toserve us, but obstacles or restrictions mentioned in the fine print or omitted entirely may prevent easyresolution of our problems. While users are now less likely to resort to doing their own programming thana decade ago, there are still many computational problems that require such brute-force efforts.Furthermore, the existence of commercial software that solves only one problem is not necessarily helpful;it is difficult to justify spending hundreds of dollars to solve a problem that may be a small part of alarger task.An annoying aspect of today’s rapidly developing computer world, at least from the point of view of thecomputist — the person who must perform calculations — is the constant stream of statements, articles,lectures and papers that describe "new, improved" hardware or software. The realities of life in the worldof technical computation, be it in engineering, natural sciences, economics, statistics or business, are thatfunds are not available to acquire each new piece of apparently useful electronics or program code.Furthermore, the cost of learning and evaluating a single new product is high.
The pressure to bring outa new product ahead of competitors is such that errors are probably present in the first (or second or thirdor . . . ) models delivered. This leads to contradictory evaluations of products in the literature, forcingprospective users to spend much valuable time and effort to discover the true utility of the product fortheir own situation.There is, of course, pressure among the user’s own community to use the "latest and best." Salespeople,industry writers and futurists have successfully created a collective faith in the ongoing rapid change incomputing. New products are supposedly obsolete as soon as they are delivered. While we all like to bemodern and up-to-date, much of the panic and hurrah is a myth.
The truth is no less interesting, but doesnot have the glamour and air-brush artwork that should, in any event, be left for the cover of fashionmagazines.We have studied computation and performed calculations for more than twenty-five years. In that time,many new and interesting devices have been brought to market. There have been substantial decreasesin the real costs of computing. In 1968, we paid $200 (Canadian) for a second-hand Monroe hand-crankedmechanical calculator. In 1980, we bought the Sharp PC 1211/Radio Shack Pocket Computer for $279(Canadian). This machine was capable of quite sophisticated programs in BASIC and had a largerepertoire of special functions.
In 1992, a modest PC with 640K memory and floppy disk drives can bebought for under $500 (Canadian) and a PC/AT with fixed disk for under $1000. Clearly, these are greatadvances, and the Monroe is now a fondly regarded antique that nevertheless still functions perfectly.
Inits time it fulfilled a need and was used to solve many problems similar to those still coming across ourdesk today. In turn, the other machines will serve their time before being replaced. In fact we disposedof our first generation personal computers late in 1991 after over 13 years of solid service.The useful lifetime of computers continues to be several years. There are sound business and operationalreasons for this. One cannot consider equipment with a useful lifetime of less than five years as a goodinvestment, though we may expect the uses of equipment to change over that lifetime. Similarly,manufacturers wish to convince us that their products are the last word in technology, but must have longenough production runs to keep their costs to a minimum. Thus many "innovations" are cosmetic and1: INTRODUCTION AND PURPOSE3designed to respond to marketing pressures.In the practice of computation the changes observed in the last twenty-five years have been quite gradual.Several commendable efforts have been made to produce quality mathematical software packages andlibraries.
Despite the success of some of these efforts and the appearance of several new journals dedicatedto specialized computation, there is still a vast body of very low quality programs in use that have beenpurchased, borrowed or stolen. These have frequently been installed without regard to the effects that adifferent computing environment may introduce into a calculated result.1.2GoalsTo the chagrin of developers of quality mathematical software, poorly designed programs will correctlysolve more than 99% of the problems presented to them. The expense and effort of good programdevelopment is spent mostly to prevent disaster for a few cases in a million.
This "insurance" aspect ofquality software is difficult to sell to users. A user who is happy with, but ignorant of, results from a poorprogram is unlikely to change programs if it means, as it usually does, a considerable effort and cost.Knowledgeable staff are seldom available to help the scientific user in the implementation of programsto carry out calculations. Unlike programs to process data or control functions, the results ofcomputational programs are rarely right or wrong absolutely.
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