Date: Sun, 6 Jun 2004 23:38:43 -0700 From: David Schultz <das@FreeBSD.ORG> To: "Steven G. Kargl" <kargl@troutmask.apl.washington.edu> Cc: freebsd-standards@FreeBSD.ORG Subject: Re: standards/59797: Implement C99's round[f]() math fucntions Message-ID: <20040607063843.GB13248@VARK.homeunix.com> In-Reply-To: <200406070128.i571SNuN068542@troutmask.apl.washington.edu> References: <20040605224915.GA3306@VARK.homeunix.com> <200406070128.i571SNuN068542@troutmask.apl.washington.edu>
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On Sun, Jun 06, 2004, Steven G. Kargl wrote: > I would have to go back and review the PR for all the discussion, > but I thought bde had proposed using rint(3) with an appropriate > rounding mode. Anyway, whatever you decide to do is fine with > me. I found that setting the rounding mode and calling rint(3) is significantly slower on x87, and that's not counting the special handling for the halfway cases. The bit-fiddling approach is a little bit faster than yours (I compared against ceil()), but it's much harder to maintain. Consider that rintf() still has bugs, and it has been around for over a decade! > I looked at the glibc implementation of round(). It does > bit twiddling, but I would definitely recommend not using > the glibc version because of licensing and possible copyright > infringement concerns [hiint compare glibc's round() with > fdlibm's ceil()]. Hmmm...the glibc implementation does indeed appear to be plagiarized. Perhaps someone should let the glibc folks know.
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