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From: Robert A Duff <bobduff@world.std.com>
Subject: Re: Matrix Multiplication
Date: 1999/12/16
Message-ID: <wccso12zxeh.fsf@world.std.com>#1/1
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Sender: bobduff@world.std.com (Robert A Duff)
References: <385699B5.59C14D03@lmco.com> <838koc$b6d$1@nnrp1.deja.com>
 <3857E220.26AE90BB@lanl.gov> <8390te$ksp$1@nnrp1.deja.com>
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Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada,comp.lang.fortran
Date: 1999-12-16T00:00:00+00:00
List-Id: <comp.lang.ada>

"William B. Clodius" <wclodius@lanl.gov> writes:

>...If I remember correctly, Ada requires
> either copy-in/copy-out or call by reference semantics by the compiler
> (without specifying the choice made) in most contexts, ...

I believe RM-6.2(12) allows substantially more freedom to the compiler
than that.  But you are correct that it's not *quite* as much freedom as
Fortran allows.  Pretty close, though, I think.

>...while Fortran
> requires that code allow either copy-in/copy-out or call by reference
> implementation, but does not require that the actual implementation be
> consistent with either semantics, i.e. at arbitrary points in the
> procedure arguments can be copied-in/copied-out without synchronizing
> with other copy-ins/copy-outs. ...

Anyway, there's an important non-technical issue: How much money are
people willing to expend on making optimizing compilers.

- Bob