On 7 February 2010 20:10, Peter Jeremy <peterjer...@acm.org> wrote: > On 2010-Feb-04 23:56:27 +0000, "Dr. David Kirkby" <david.kir...@onetel.net> > wrote: >>There is another maths library which can be linked, rather than using >>-lm. That at least got around this for the previous case of this. > > For that matter, if anyone is aware of a suitably licensed C99 libm, > I'd also be interested.
No sorry, > Since we're seeing various numeric noise in the double-precision > results, what assurance do we have that the 'expected' results are > actually correct? Have they been independently verified or are they > just what was reported by a particular Sage build? One I know of was E raised to the power of 1.0, so should have been E. So the exact result is known. I also found that Mathematica would give the same result as sage on the calculation using a SPARC unless Mathematica was also set to use slower but more accurate extended precision. >>Ultimately, the FPU uses 64-bit, whereas that in the Intel chip works >>to 80-bits internally, but 64-bit when the data is read out. I think >>inherently the SPARC chip is less accurate. > > Well, the x87 FPU natively works in 80-bit mode. On the downside, > this means that using C doubles (64-bit) in conjunction with the x87 > FPU results in double-rounding - which can also cause problems. > AFAIK, only the 32-bit x86 API uses the x87 and the x86_64 API > defaults to MMX mode (64-bit). I'll take your word for that. > And the SPARC architecture defines a 128-bit 'long double', though I'm > not sure what chips implement it. If that is so, then I would expect 't2' would implement this, since its the latest generation chip so would have to for reasons of backward compatibility. But that said, floating point performance is of no real issue in the market for which 't2' was designed. > It's (theoretically) possible to deliver correctly rounded 64-bit > results using either the SPARC or x87 FPU. Doing so will need > diffferent algorithms and the SPARC will probably be slower. Especially if it is 't2'!! Dave -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
