Date: Sun, 6 Jun 2004 18:33:53 -0700 (PDT) From: "Steven G. Kargl" <kargl@troutmask.apl.washington.edu> To: David Schultz <das@FreeBSD.ORG> Cc: freebsd-standards@FreeBSD.ORG Subject: Re: standards/59797: Implement C99's round[f]() math fucntions Message-ID: <200406070133.i571Xrxu068576@troutmask.apl.washington.edu> In-Reply-To: <20040605025359.GA3084@VARK.homeunix.com>
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David Schultz wrote: > > BTW, benchmarking shows that using the sample implementation that > appears in the C99 standard results in a slowdown of two orders of > magnitude over your round() implementation and four orders of > magnitude over the x87 frndint instruction. Just setting the > rounding mode and calling rint() also results in a significant > slowdown. Thus, we definitely want something that's in the spirit > of what you wrote, but perhaps one that operates on the bits directly. > 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()]. -- Steve http://troutmask.apl.washington.edu/~kargl/
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