Date: Sat, 14 Jul 2001 13:23:41 -0500 From: Stephen Montgomery-Smith <stephen@math.missouri.edu> To: Jim.Pirzyk@disney.com Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: math library difference between linux emulation and native freebsd (and native linux) Message-ID: <3B508E2D.41FAC546@math.missouri.edu> References: <200107141809.f6EI9M809946@snoopy.fan.fa.disney.com>
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The correct answer to the level of accuracy you quote is:
137581029243568295877658.36934931
Both are correct to about 15 sig figs, which is about what the precision
of IEEE double precision arithmetic is supposed to be.
Jim.Pirzyk@disney.com wrote:
>
> So I have stumbled across a linux emulation bug in freebsd. Below
> is the program that returns different results based on FreeBSD,
> Linux or Linux emulation under FreeBSD.
>
> Running natively under FreeBSD:
>
> x = 53.27850000
> exp(x) = 137581029243568449912832.00000000
>
> Running natively under Linux:
>
> x = 53.278500
> exp(x) = 137581029243568449912832.000000
>
> Running under FreeBSD in Linux emulation mode:
>
> x = 53.27850000
> exp(x) = 137581029243567812378624.00000000
>
> #include <stdio.h>
> #include <math.h>
> #include <stdlib.h>
>
> int main (int argc, char **argv) {
> double x = 53.278500;
>
> printf ("x = %8lf\n", x);
> printf ("exp(x) = %8lf\n", exp(x));
>
> exit (0);
> }
>
> There are only two shared libaries in common (libc and libm) and
> both are the same on FreeBSD (in /compat/linux) and Linux.
>
> So any ideas on where the program is going wrong?
>
> - JimP
> --
> --- @(#) $Id: dot.signature,v 1.10 2001/05/17 23:38:49 Jim.Pirzyk Exp $
> __o Jim.Pirzyk@disney.com ------------- pirzyk@freebsd.org
> _'\<,_ Senior Systems Engineer, Walt Disney Feature Animation
> (*)/ (*)
>
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--
Stephen Montgomery-Smith
stephen@math.missouri.edu
http://www.math.missouri.edu/~stephen
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