float128 are 16 bytes wide but have the structure of x87 80-bits + extra 6 bytes for alignment: >From "http://lwn.net/2001/features/OLS/pdf/pdf/x86-64.pdf": "... The x87 stack with 80-bit precision is only used for long double."
And: >>> e47 = float128(1e-47) >>> e30 = float128(1e-30) >>> e50 = float128(1e-50) >>> (e30-e50) == e30 True >>> (e30-e47) == e30 False >>> This shows that float128 has no more then 19 digits precision Nadav. -----הודעה מקורית----- מאת: [EMAIL PROTECTED] בשם Robert Kern נשלח: ג 09-דצמבר-08 22:40 אל: Discussion of Numerical Python נושא: Re: [Numpy-discussion] Importance of order when summing values inanarray On Tue, Dec 9, 2008 at 09:51, Nadav Horesh <[EMAIL PROTECTED]> wrote: > As much as I know float128 are in fact 80 bits (64 mantissa + 16 exponent) so > the precision is 18-19 digits (not 34) float128 should be 128 bits wide. If it's not on your platform, please let us know as that is a bug in your build. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
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