Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Re: Missing the whole point (the Fortran vs. C debate)
Message-ID: <8084@lanl.gov>
Date: 6 Dec 90 19:51:08 GMT
References: <9424@ncar.ucar.edu>
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 19

From article <9424@ncar.ucar.edu>, by morreale@bierstadt.scd.ucar.edu (Peter Morreale):
> [...]
>     The Cray Fortran compilers will vectorize *every* loop (which meets
>     vectorization criteria) by default.  The programmer doesn't need to
>     make any modifications to his code.  (although most do to obtain
>     increased performance, but non-portable constructs are not used or
>     needed)

This is not _quite_ true.  It is true that the Cray compilers have
always been able to vectorize _some_ loops automatically.  But, it
took many years for them to come to the degree of effectiveness it
has today.  Further, _some_ loops actually have dependencies, but
some of the algorithms which have such loops are stable if the loop
is vectorized anyway - for such cases, the CDIR$ NODEP directive
exists.  Finally, of course, there is also a directive which tells
the compiler _not_ to vectorize.  So, what you say is true to an extent,
but so was the comment you were responding to.

J. Giles