Date: Sat, 14 Jul 2001 14:43:57 -0500 From: Stephen Montgomery-Smith <stephen@math.missouri.edu> To: jmcoopr@webmail.bmi.net Cc: Jim.Pirzyk@disney.com, freebsd-hackers@FreeBSD.ORG Subject: Re: math library difference between linux emulation and native freebsd (and native linux) Message-ID: <3B50A0FD.4E501941@math.missouri.edu> References: <200107141907.MAA07030@smtp.bmi.net>
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jmcoopr@webmail.bmi.net wrote: > > > >I also tried the same experiment with sin and gamma - then the problem > >does not occur. Well except that the answer for gamma(53.278500) is > >reported as 157.464664 which is way wrong. > > >When I tried it for x=52 they gave almost the same answer, only > >seperated by the last bit (the decimal versions were reported as the > >same). For x=54 they both gave the same wrong answer 160.331128. > > >I don't know a whole lot about IEEE. What is the largest number it is > >supposed to handle? Looking at man math it says it should handle > >numbers as large as 1.8e308 - we certainly are not in that range!!! > > But remember, floating point is DIFFERENT--nothing is exact. You can > create a number with a magnitude about 1.8e308, but you sure don't get > 308 significant digits. You missed my point (or I didn't explain it well). I was wondering if the problem was because we were dealing with such large numbers that the arithmetic got out of wack. exp(54) = 160.331128 is way way wrong, by orders of magnitude. Same for gamma(53.27850) = 157.464664. My point is that the correct answers are way less than 1e308, so there is no excuse for the wrong answers. By the way, Mathematica, which is Linux binary running under emulation, gets the answers correct. -- Stephen Montgomery-Smith stephen@math.missouri.edu http://www.math.missouri.edu/~stephen To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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