Path: utzoo!attcan!uunet!husc6!uwvax!oddjob!ncar!ames!mailrus!cornell!uw-beaver!teknowledge-vaxc!sri-unix!garth!smryan
From: smryan@garth.UUCP (Steven Ryan)
Newsgroups: comp.arch
Subject: Re: getting rid of branches
Message-ID: <853@garth.UUCP>
Date: 1 Jul 88 21:01:12 GMT
References: <1941@pt.cs.cmu.edu> <3208@ubc-cs.UUCP> <1986@pt.cs.cmu.edu> <91odrecXKL1010YEOek@amdahl.uts.amdahl.com> <12258@mimsy.UUCP>
Reply-To: smryan@garth.UUCP (Steven Ryan)
Organization: INTERGRAPH (APD) -- Palo Alto, CA
Lines: 22

>                                                How do you move old
>code (`dusty decks') onto a parallel processor?  One way is to slice up
>the program into independent pieces that can be combined again later.
>          .   .   .
>you run two or three loops:
>
>		1			2			3
>
>	for i in [0..n-1)	for i in [0..n-1)	for i in [0..n-1)
>		A := compute		A := compute		A := compute
>		B[i] := fn1(A)		B[i] := fn2(a)		combine[i] :=
>									test(A)
>	rof			rof			rof

On a 205, if compute, test, and fn1 and fn2 are vectorisable, this entire
construct can be hand-vectorised by something like
               compute' -> promoted A'
               test(A') -> bit vector
               fn1'(A') -> B[i] if bit[i] set (else discard and ignore faults)
               fn2'(A') -> B[i] if bit[i] clear (else discard and ignore faults)
CFT is supposed to provide a vectorisable conditional expression. FTN200 code
to vectorise ifs may/may not be completed and released.