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From: "Steven G. Kargl" <kargl@troutmask.apl.washington.edu>
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To: David Schultz <das@FreeBSD.ORG>
Date: Sun, 6 Jun 2004 18:33:53 -0700 (PDT)
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cc: FreeBSD-gnats-submit@FreeBSD.ORG
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Subject: Re: standards/59797: Implement C99's round[f]() math fucntions
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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/