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From: david@titan.rice.edu (David Callahan)
Newsgroups: comp.lang.fortran,comp.software-eng
Subject: Re: Fortran follies
Message-ID: <1555@kalliope.rice.edu>
Date: 24 Jun 88 21:35:49 GMT
References: <5377@cup.portal.com> <2852@mmintl.UUCP> <1005@cresswell.quintus.UUCP> <701@garth.UUCP> <2157@sugar.UUCP>
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Reply-To: david@titan.rice.edu (David Callahan)
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In article <2157@sugar.UUCP> ssd@sugar.UUCP (Scott Denham) writes:
>In article <701@garth.UUCP>, smryan@garth.UUCP (Steven Ryan) writes:
>> 
>> Assuming all dummy arrays are assumed-size (largest dimension is *) breaks
>> vectorisers and optimisers which need to know the array size. (This has to
>> do with dependency analysis.)
>
>You make a good point. 

I'm not sure about that. Vectorizers will only rarely need the largest
dimension since it does not appear in the addressing arithmetic. For that
reason it probably will not be used by the decision procedure which
determines if a pair of references to a particular variable overlap and
so will not influence vectorization. Furthermore, unless the bound
is hardwired as a constant, it won't be very useful anyway. If you
see reduced vectorization it may be due to an assumption that the
dimension is short and hence vectorization would be unprofitable.

David Callahan
Rice University