Date: Mon, 8 Feb 2021 23:34:12 +0100 From: Dimitry Andric <dim@FreeBSD.org> To: Alexander Richardson <arichardson@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 93fc67896550 - main - Fix incorrect powf(3) result with x near 1 and |y| much larger than 1 Message-ID: <A8B85EB3-C908-409F-9F89-56541E2C4A16@FreeBSD.org> In-Reply-To: <CA%2BZ_v8qfoqj7FRk5U=C7_T%2B%2BW-dD4V_NzE16d0fvR2kVDTqarA@mail.gmail.com> References: <202102081949.118Jn10U008133@gitrepo.freebsd.org> <CA%2BZ_v8qfoqj7FRk5U=C7_T%2B%2BW-dD4V_NzE16d0fvR2kVDTqarA@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
[-- Attachment #1 --] On 8 Feb 2021, at 23:09, Alexander Richardson <arichardson@freebsd.org> wrote: > > On Mon, 8 Feb 2021, 19:49 Dimitry Andric, <dim@freebsd.org> wrote: > The branch main has been updated by dim: > > URL: https://cgit.FreeBSD.org/src/commit/?id=93fc67896550548f91b307dbe3053f11db5d4a8a > > commit 93fc67896550548f91b307dbe3053f11db5d4a8a > Author: Steve Kargl <sgk@troutmask.apl.washington.edu> > AuthorDate: 2021-02-08 19:45:30 +0000 > Commit: Dimitry Andric <dim@FreeBSD.org> > CommitDate: 2021-02-08 19:48:43 +0000 > > Fix incorrect powf(3) result with x near 1 and |y| much larger than 1 > > This adjusts the check to trigger overflow/underflow to a slightly lower > value. > > Before: powf(9.999995e-01, -1.342177e+08) -> inf > After: powf(9.999995e-01, -1.342177e+08) -> 1.858724e+31 > > MFC after: 1 week > --- > lib/msun/src/e_powf.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/msun/src/e_powf.c b/lib/msun/src/e_powf.c > index 53f1d37d6bec..33eedad50b16 100644 > --- a/lib/msun/src/e_powf.c > +++ b/lib/msun/src/e_powf.c > @@ -136,7 +136,7 @@ __ieee754_powf(float x, float y) > /* |y| is huge */ > if(iy>0x4d000000) { /* if |y| > 2**27 */ > /* over/underflow if x is not close to one */ > - if(ix<0x3f7ffff8) return (hy<0)? sn*huge*huge:sn*tiny*tiny; > + if(ix<0x3f7ffff7) return (hy<0)? sn*huge*huge:sn*tiny*tiny; > if(ix>0x3f800007) return (hy>0)? sn*huge*huge:sn*tiny*tiny; > /* now |1-x| is tiny <= 2**-20, suffice to compute > log(x) by x-x^2/2+x^3/3-x^4/4 */ > > > Do we have a test with previously buggy values? If not it would be good to add one. Nope, I'll see if I can grok the awful kyua stuff enough to add it. -Dimitry [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.2 iF0EARECAB0WIQR6tGLSzjX8bUI5T82wXqMKLiCWowUCYCG8ZAAKCRCwXqMKLiCW ox1xAKDif7gyRNSkSUrzQJUdg9YNE/j9bACguwOPczcPPbWMZeHpF8OsuobRZys= =wh56 -----END PGP SIGNATURE-----
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?A8B85EB3-C908-409F-9F89-56541E2C4A16>