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From: loren@pixar.UUCP (Loren Carpenter)
Newsgroups: comp.lang.c,comp.arch
Subject: Re: Explanation, please!
Keywords: Duff Loop
Message-ID: <2361@pixar.UUCP>
Date: 1 Sep 88 02:13:17 GMT
References: <638@paris.ics.uci.edu> <dpmuY#2EBC4R=eric@snark.UUCP> <8389@smoke.ARPA>
Reply-To: loren@pixar.UUCP (Loren Carpenter)
Organization: Pixar -- Marin County, California
Lines: 12

The Duff Loop (as far as I know) was first cast into C by Tom Duff when
he was at Lucasfilm in the early 1980's.  We used it at Lucasfilm wherever
we needed reasonable speed without resorting to assembly language.  It
obviously generalizes to more than memory copy & clear.

I and others have used this control construct for many years, but always
in assembly language.  I learned it from Howard Schmeising at Boeing in 1969,
where we were writing optimal stack code for CDC 6600's (a $7M RISC machine).
We could get 5+ 60-bit Mflops if we worked at it.

			Loren Carpenter
			...{ucbvax,sun}!pixar!loren