Date: Sat, 6 Feb 2021 14:13:53 -0800 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Dimitry Andric <dim@freebsd.org> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: hypothl(x) mishandles subnormal numbers. Message-ID: <20210206221353.GB46087@troutmask.apl.washington.edu> In-Reply-To: <C5652F7E-A943-42AA-A70B-1D4C1C763E06@FreeBSD.org> References: <20210206203929.GA45801@troutmask.apl.washington.edu> <20210206210448.GC45801@troutmask.apl.washington.edu> <C5652F7E-A943-42AA-A70B-1D4C1C763E06@FreeBSD.org>
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On Sat, Feb 06, 2021 at 10:32:33PM +0100, Dimitry Andric wrote: > On 6 Feb 2021, at 22:04, Steve Kargl <sgk@troutmask.apl.washington.edu> wrote: > > > > On Sat, Feb 06, 2021 at 12:39:29PM -0800, Steve Kargl wrote: > >> I've long forgotten by freebsd bugzilla password. > >> So, if someone would like to submit a bug report, > >> here's a test program. > >> > > Forgot to include that issue was identified from > > a bug report in the OpenLibm bug mailing list. > > > > https://github.com/JuliaMath/openlibm/issues/224 > > I put this in <https://bugs.freebsd.org/253313>. Now the trick is to > figure out what is going on in e_hypotl.c... :) > Thanks. I took a quick look, and there seems to be some magic scaling happen. hypotl(x,y) should compute sqrtl(x*x+y*y) while avoiding overflows and underflows. I suspect that the scaling needs to be tweaked. It may take me a bit to work out how to fix it. -- Steve
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