Path: utzoo!attcan!uunet!mcsun!ukc!warwick!nott-cs!ucl-cs!news
From: G.Joly@cs.ucl.ac.uk (Gordon Joly)
Newsgroups: comp.software-eng
Subject: Re: Tolerance
Message-ID: <1419@ucl-cs.uucp>
Date: 6 Feb 91 12:52:34 GMT
Sender: news@cs.ucl.ac.uk
Lines: 34


cwk@ORCRIST.GANDALF.CS.CMU.EDU (Charles Krueger) writes

> How about weather predictions?  In fact, any time software simulates an
> external reality (this includes numerical analysis), the input and output
> abstractions are probably approximations.  The designer, programmer, and
> user should all understand that there are tolerances.  These tolerances
> should be quantified.
> 
> What goes on inside the computer, however, is still as precise as ever.

Yes, I think that is true. Digital computers, at the bit level are
precise, but I feel sure that genetic algorithms need their fill of a
Really Good Random Number Generator. Also, Monte Carlo methods and
simulated annealing have a need for randomness.

Wheather "predictions" are doomed to failure once they find a chaotic
path in the solution space.

dave@cs.arizona.edu (Dave P. Schaumann) writes:

> I'd certainly be interested in hearing a discussion on this topic (tolerance
> implicit in software).
> 
> Numerical analysis aside, I can't imagine a single instance of "close is 
> good enough".

Implicit? What is implicit should be made explicit! SDI has the
problem of being implicitly faulty, but that has not stopped the
current rebirth.

Gordon Joly                                       +44 71 387 7050 ext 3716
Internet: G.Joly@cs.ucl.ac.uk          UUCP: ...!{uunet,ukc}!ucl-cs!G.Joly
Computer Science, University College London, Gower Street, LONDON WC1E 6BT


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