Mailinglist Archive: opensuse (3337 mails)

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Re: [Fwd: Re: [SLE] Real Numbers representation in Tcl language]
  • From: Jerry Feldman <gaf@xxxxxxx>
  • Date: Fri, 14 Apr 2006 08:23:45 -0400
  • Message-id: <200604140823.45755.gaf@xxxxxxx>
On Thursday 13 April 2006 9:05 pm, Ken Jennings wrote:
> On Thursday 13 April 2006 10:36, Jerry Feldman wrote:
> > On Wednesday 12 April 2006 6:32 pm, Greg Wallace wrote:
> > > On Wednesday, April 12, 2006 @ 2:30 PM, John E. Perry wrote:
> > > >Sorry Greg, I forgot the SLE reply-to quirk.
> > >
> > > No problem. I didn't realize the program used software to elevate
> > > the values for ordinates and mantissas beyond the machine's hardware
> > > limits. Very interesting. I'm obviously way behind the times on how
> > > math functionality is implemented in the modern PC era! Good info.
> >
> > This has always been true. Today, 128 bit long doubles are generally
> > done in software.
> > Additionally, some IEEE functionality is implemented in software.
> > For instance, most floating point numbers are stored in normalized
> > format, but there are numbers greater than 0.0 but less than the
> > minimum normalized number that generally require software. These are
> > called denormals, and those are one of the reasons that most compilers
> > generate "fast floating point" by default because strict IEEE
> > compliance can be very slow.
>
> What type will designate some kind of floating point value as 128-bit?
>
> Here sizeof long double == 12 bytes (96 bits) on Amd Athlon XP 2500+
Implementation defined. On my 32-bit workstation is it 96 bits, on 2
different Linux 64-bit systems it is 128 bits (IA64 and X86_64)

IA64 RHEL 4.0
[gaf@cedar C]$ ./ldsize
Sizeof long double is 16

SuSE 10 32-bit system
gaf@sauron:~/src/C> gcc ldsize.c -o ldsize
gaf@sauron:~/src/C> ./ldsize
Sizeof long double is 12

td190> ./ldsize
Sizeof long double is 16
td190> uname -a
Linux td190 2.6.5-7.252-smp #1 SMP Tue Feb 14 11:11:04 UTC 2006 x86_64
x86_64 x86_64 GNU/Linux
--
Jerry Feldman <gaf@xxxxxxx>
Boston Linux and Unix user group
http://www.blu.org PGP key id:C5061EA9
PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9

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