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Re: FWD: FLOATING-POINT CONSISTENCY, -FFLOAT-STORE, AND X86
- To: Tim Hollebeek <tim at wagner dot princeton dot edu>
- Subject: Re: FWD: FLOATING-POINT CONSISTENCY, -FFLOAT-STORE, AND X86
- From: hjstein at bfr dot co dot il (Harvey J. Stein)
- Date: 16 Dec 1998 23:04:19 +0200
- CC: pcg at goof dot com (Marc Lehmann), egcs at cygnus dot com
- CC: hjstein at bfr dot co dot il
- References: <199812162050.PAA17917@wagner.Princeton.EDU>
Tim Hollebeek <tim@wagner.princeton.edu> writes:
> Marc Lehmann writes ...
> >
> > I still don't see what the 64 bit precision idea gives us, in terms of
> > performance. First, it doesn't give us full ieee, second, it kills
> > performance, depending on where the rounding mode is set (before each
> > assignment? resetting it to normal before each long double assignment?)
>
> 64 bit rounding is a wonderful solution .... assuming the only
> floating point type you ever use is 'double'. As such, it makes sense
> as a practical user level solution, but I'm afraid it's almost useless
> as a general purpose solution.
As I just detailed, I don't think it's any worse wrt correct numerics
than using 80 bit FPU + 80 bit spills.
--
Harvey J. Stein
BFM Financial Research
hjstein@bfr.co.il