Re: mathlib pow gives bad result
Re: mathlib pow gives bad result
- Subject: Re: mathlib pow gives bad result
- From: Lance Westerhoff <email@hidden>
- Date: Fri, 19 May 2006 09:24:38 -0400
Hi Tomas-
I would suggest you also post this question to Apple's Scitech list
(see link below). (a) There are actually Apple scitech library
developers on the list who can comment/bugfix/etc and (b) there are a
ton of people on the list who develop schtech software for any number
of architectures and who could comment precision differences.
http://lists.apple.com/mailman/listinfo/scitech
It's a good group of folks. Hope that helps!
-Lance
On May 19, 2006, at 6:56 AM, email@hidden wrote:
Dear Darwin developers,
I've discovered that my program works differently on PowerPC
running Mac OS
X 10.4.6 and Itanium2 running HP-
UX. The problem appears to be in the pow function which gives
result that
differs by 12 ulps from Itanium2.
PowerPC-Mac OS X double: 0.44921455671723881 (gdb> print val)
Itanium2-HP UX double: 0.44921455671723876 (gdb> print val)
Mathematica (PowerPC-double): 0.44921455671723886 649004953142139
(N[val,32])
Mathematica (Pentium4-double): 0.44921455671723875 546774706890574
(N[val,32])
Mathematica (rational evaluation): 0.44921455671723877 615723308414713
(N[val,32])
Itanium2 is obviously closer to the proper result. Should I file a bug
against libm?
Thanks,
Tomas
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