Date: Sun, 8 Jul 2012 11:51:56 -0600 From: Warner Losh <imp@bsdimp.com> To: David Schultz <das@freebsd.org> Cc: freebsd-current@FreeBSD.ORG, Peter Jeremy <peter@rulingia.com>, Steve Kargl <sgk@troutmask.apl.washington.edu> Subject: Re: Use of C99 extra long double math functions after r236148 Message-ID: <210816F0-7ED7-4481-ABFF-C94A700A3EA0@bsdimp.com> In-Reply-To: <20120708124047.GA44061@zim.MIT.EDU> References: <4FC3A154.8030702@missouri.edu> <20120528203159.GA76340@troutmask.apl.washington.edu> <4FC3EBDA.2080502@missouri.edu> <20120528221731.GA76723@troutmask.apl.washington.edu> <4FC40449.3040602@missouri.edu> <20120528233035.GA77157@troutmask.apl.washington.edu> <4FC40DEA.8030703@missouri.edu> <20120529000756.GA77386@troutmask.apl.washington.edu> <4FC43C8F.5090509@missouri.edu> <20120529045612.GB4445@server.rulingia.com> <20120708124047.GA44061@zim.MIT.EDU>
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On Jul 8, 2012, at 6:40 AM, David Schultz wrote: > On Tue, May 29, 2012, Peter Jeremy wrote: >> On 2012-May-28 15:54:06 -0700, Steve Kargl = <sgk@troutmask.apl.washington.edu> wrote: >>> Given that cephes was written years before C99 was even >>> conceived, I suspect all functions are sub-standard. >>=20 >> Well, most of cephes was written before C99. The C99 parts of >> cephes were written to turn it into a complete C99 implementation. >=20 > I'm a bit late to the party, but I thought I'd chime in with some > context. We did consider using Cephes years ago, and even got > permission from the author to release it under an acceptable license. > We later decided not to use it for technical reasons. >=20 > By the way, virtually none of the people who have complained about the > missing functions actually need them. Mostly they just want to > compile some software that was written by a naive programmer who > thought it would be cool to use the most precise type available. The > complex functions are even less commonly needed, and the truth is that > they have no business being part of the C standard anyway. >=20 > The question remains of what to do about the missing functions. Bruce > and Steve have been working on expl and logl for years. If those ever > get in the tree, the remaining long double functions are easy. Those > functions are basically done, modulo a bunch of cleanup and testing, > and I encourage any mathematically inclined folks who are interested > in pushing things along to get in touch with them. I'm not going to > have any time myself for a few months at least. Where can I find these? > Lastly, there's the question of mediocre alternatives, such as > solutions that get the boundary cases wrong or don't handle 128-bit > floating point. For the exponential and logarithmic functions, Bruce > and Steve have already written good implementations, so there's no > reason to settle for less. As for the other long double functions, > bringing in some Cephes code in a separate directory as a temporary > fix might be the way to go. I don't like that solution, and Steve > raises some good technical points about why it isn't ideal; however, a > better solution is more than a decade overdue, and people are > justified in finding that unacceptable. Don't let the perfect be the enemy of the good. It is better to have OK = implementations of these functions than none at all. We originally had = so-so double support, but bruce spent many years optimizing them to make = them very good. If we were just starting out, and hadn't let 10 years = get behind us, I'd give the substandard argument some weight. But now = that we're 13 years down the line from c99's publication I think we need = to relax our standards a bit. I'd even argue that these functions being = a little bad could easily spur people to make them better. Their = absence makes people just #define llexp(x) lexp(x), etc. :( Warner Warner=
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