Date: Sat, 14 Jul 2001 11:28:03 -0700 From: Jim Pirzyk <Jim.Pirzyk@disney.com> To: jmcoopr@webmail.bmi.net Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: math library difference between linux emulation and native freebsd (and native linux) Message-ID: <iss.450f.3b508f31.639ad.1@mercury.fan.fa.disney.com> In-Reply-To: <200107141819.LAA06370@smtp.bmi.net>
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On Saturday, July 14, 2001, at 11:17 AM, jmcoopr@webmail.bmi.net wrote: > In <200107141809.f6EI9M809946@snoopy.fan.fa.disney.com>, on 07/14/2001 > at 11:09 AM, Jim.Pirzyk@disney.com said: > >> 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 > > My guess is difference between Linux emulation and "native" 's floating > point formatting for printf. With the number of significant digits > you're invoking, small differences in handling low order bits can be > significant. So I tried writing it out with write directly and did a binary compare, they still are different. :( - JimP To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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