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From: karl@mtu.UUCP (Karl Ottenstein)
Newsgroups: net.unix
Subject: Re:  Convex C-1 computer? --VECTORIZATION (flame)
Message-ID: <182@mtu.UUCP>
Date: Fri, 3-May-85 23:40:46 EDT
Article-I.D.: mtu.182
Posted: Fri May  3 23:40:46 1985
Date-Received: Mon, 6-May-85 01:04:43 EDT
References: <10188@brl-tgr.ARPA> <964@ames.UUCP>
Organization: Michigan Tech, Houghton, MI
Lines: 23

> Vectorization only works on certain "well structured, regular" loops.
> This is nothing new, the first FORTRAN programs did not vectorize well
> either, so you will either restructure to gain performance benefits of
> vector C (potentially non-portable) or settle for scalar performance.
> That is how most supercomputer codes are structured.  It depends how much
> work you are willing to put into it.

The issue is not that old FORTRAN programs did not vectorize well, but
rather that old compilers did not perform sufficient analysis to produce
good code.  The work of Kuck (et al) at Illinois and Kennedy (et al) at
Rice has produced very powerful vectorizing techniques which are incorporated
in several commercial translators, including [I am led to believe] the
Convex compiler.

It is true that Cray manuals specified that loops should look certain ways
to be vectorized, but that was simply due to their stupid compilers at the
time.
-- 

		Karl Ottenstein
		Michigan Technological University
		uucp: {lanl, ihnp4, glacier}!mtu!karl
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