long double (was "strtold?")

Tim Prince TimothyPrince@sbcglobal.net
Wed Mar 18 07:56:00 GMT 2009

Howland Craig D (Craig) wrote:
>> Jeff Johnston wrote:
>>>      (By the way, so far for the math library I have ceill, floorl,
>>> nearbyintl, rintl, truncl, fpclassify, and some of the other similar
>>> easy ones.  They basically function but need polish.  I will need
> some
>>> kind of help for the numerical (e.g. sine, log) functions as I don't
>>> know enough to write them.  Anyone who'd like to help, let me know.)
>> It can definitely be a can of worms regarding accuracy as the mathfp
>> experiment has proven.
>> A number of the libm routines were originally taken from Sun.  You
> might
>> want to check if there are
>> already long double versions out there from Sun if you haven't already
>> done so.
>      I have done some looking, and was not finding much; I've found one
> or two candidates, but not a whole set like I had expected.  (For
> example, FreeBSD has just the easy ones like those I've mentioned.)
> I'll
> do more searching later.  Hopefully people can keep it in mind and maybe
> we'll stumble across a set that we can import.  I had hoped to find a
> set under OpenSolaris, but they don't appear to have the math library
> visible.
>      I share your concern about checking.  Related to that, I did find
> an arbitrary-precision package that has the transcendentals that could
> be used for checking.
>                 Craig
How ambitious are you?  Does it need to be as difficult to read as 
fdlibm?  Both 80-bit and 128-bit IEEE formats?  For x86 80-bit, gcc/387 
in-lines are good enough, although expl() and powl() could use something 
a notch better than glibc.  If you're trying to be more general, it's 
difficult to be efficient as well.  For comparison checks, are you 
satisfied with gmp/mpfr, or is their use in gcc a disrecommendation?  
There are test suites, elefunt/celefunt being among the better/longer 

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