Re: Arithmetic accuracy, was Compiler bugs (John Dallman)
24 Jan 2002 14:53:17 -0500

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From: (John Dallman)
Newsgroups: comp.compilers
Date: 24 Jan 2002 14:53:17 -0500
Organization: By appointment only
References: 02-01-081
Keywords: arithmetic
Posted-Date: 24 Jan 2002 14:53:17 EST (Nick Maclaren) wrote:

> Firstly, numerical experts do NOT depend on such things, because they
> know better. One of their main objections (sic) to consistent
> floating-point is that it is extremely harmful in many important ways,
> and it leads non-experts to believe that their answers are right
> because they are the same on multiple systems. I see this delusion
> regularly.

I think anyone would feel entitled to object to the explanation I once
got in a presentation from a processor manufacturer to the effect that
"This set of floating-point instructions on this processor is not
guaranteed to produce results consistent with this other, overlapping,
set of floating point instructions at the same precision on this same
processor". To make it extra worrying, they tried to flip over that
slide to fast for anyone to read. However, it fortunately turned out
that the people who wrote the presentation didn't know what they were
talking about.

No brand names, no packdrill.

John Dallman
                    "C++ - the FORTRAN of the early 21st century."

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