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Re: long double (was "strtold?")


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 established.


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