site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com On Fri, 2006-05-19 at 06:56 -0400, zahradnicky@kppm.cz 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?

If Itanium2 does x86 floating point arithmetic, keep in mind that x86 operates on 80 bit floats internally, while ppc (afaik) does "only" work with the given 64 bit. So this probably is an architecture issue. You could try and compare this to linux/ppc results (via a ppc/linux live-cd perhaps). If precision is a general problem for you, you might try some software implemented multi-precision floating point numbers, e. g. gmp [1]. -Markus [1] http://www.swox.com/gmp/ -- http://www.mweissmann.de/ http://www.opendarwin.org/~mww/ _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... This email sent to site_archiver@lists.apple.com