Re: Who uses clapack?

From: glen herrmannsfeldt (gah_at_ugcs.caltech.edu)
Date: 12/11/04 

Date: Sat, 11 Dec 2004 09:26:11 GMT

Greg Lindahl wrote:
(snip)

> Wow. I can't believe anyone would post this to sci.math.num-analysis!
> I thought that non-explicit use of extended precision variables was
> universally considered to be a dumb idea. If you want explicit use
> of extended precision with LAPACK, you need extra functions.

> BTW, modern compilers on PCs generally default to using SSE2
> instructions on modern PC cpus, hence no more extended precision
> unless you ask for it. This became true soon after the Pentium 4 was
> released, which was a few years ago.

As far as I know, about half the time the extra precision helps,
and about half the time it hurts. (It hurts when things
round the wrong way, or when quantities that should be equal
are not equal.)

-- glen

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