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Date: Tue, 29 Jan 2019 12:43:08 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Cc: Damian McGuckin <damianm@....com.au>
Subject: Re: Possible Mistype in exp.c
* Damian McGuckin <damianm@....com.au> [2019-01-29 22:26:23 +1100]:
> On Tue, 29 Jan 2019, Szabolcs Nagy wrote:
>
> > it's not the division that's supposed to raise the exception,
> > but the cast (although the division might in case of an x with
> > sufficiently large magnitude).
>
> I did not think about that. An interesting approach.
>
> > in any case i plan to completely rewrite exp and other
> > important math functions:
> >
> > https://www.openwall.com/lists/musl/2018/12/08/1
>
> Thanks for the pointer.
>
> > that implementation is >2x faster in general than the old fdlibm code as
> > well as more precise.
>
> It is hard to argue to 2x faster. Mind you, I certainly found the ARM code
> much harder to read. Interesting none the less.
i did some cleanups compared to the arm repository:
https://www.openwall.com/lists/musl/2018/12/08/3/7
so e.g. some of the ifdef config variants got removed,
if you have some particular idea what could be improved
then let us know.
(the special case handling is more complicated because
it tries to avoid double rounding in the subnormal range,
the old code had >0.75 ulp error in this case, the new
code is always < 0.6 ulp error, it is probably not worth
the trouble, but i tried to guarantee "almost always
correctly rounded and only near half-way results may get
incorrectly rounded" for the new implementations)
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