From: robert_dewar@my-dejanews.com
Subject: Re: should I be interested in ada?
Date: 1999/02/20
Date: 1999-02-20T00:00:00+00:00 [thread overview]
Message-ID: <7aldu1$4q$1@nnrp1.dejanews.com> (raw)
In-Reply-To: 7akvao$j5t$2@plug.news.pipex.net
In article <7akvao$j5t$2@plug.news.pipex.net>,
"Nick Roberts" <Nick.Roberts@dial.pipex.com> wrote:
> Reorder(X,J)
>
> You've got to declare a utility procedure, certainly, but
> otherwise this is just as neat as the Fortran, surely?
My goodness one would almost think that Nick was trying to
make Ada look bad by making dubious arguments. First, the
Ada code is far uglier and less safe than the Fortran code,
I really cannot imagine anyone thinking otherwise. But
more importantly, the Ada code does not catch the semantics
of the FORALL at all, there is no parallelism at all in the
Ada code, and indeed it is quite likely that not even a
clever optimizer can bail this out, because, as always it
is the exceptions that get you in Ada (if an exception is
raised, the semantics dictate exactly which iterations of
the loop have occured and which have not). Nick has
conveniently ignored this in his thinking, but it turns
out to be absolutely crucial. All sorts of loops in Fortran
that can be assumed to be parallel by the optimizer even if
FORALL is not used CANNOT be assumed to be parallel in Ada
because of the exception issue.
This means that FOR ALL is in a sense even more crucial
in Ada (which doesn't have it) than in Fortran 95 (which
does).
All this was covered in rather excruciating detail in the
thread a few years ago about implementing FOR ALL in Ada.
More so, perhaps? And it will not
> necessarily produce object code which is any less
efficient than the Fortran
> equivalent.
>
> The basic principle is that there is no Fortran 90
construct which cannot be
> modelled, perfectly adequately, by an Ada abstraction
(typically a procedure
> or function). Furthermore, you get something extra in
making that
> abstraction: encapsulation (factoring out common code),
and a degree of
> self-documentation (the name of the subprogram says what
it does).
>
> -------------------------------------
> Nick Roberts
> -------------------------------------
>
>
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next prev parent reply other threads:[~1999-02-20 0:00 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-02-14 0:00 should I be interested in ada? Phillip Helbig
1999-02-15 0:00 ` Marin David Condic
1999-02-23 0:00 ` David Starner
1999-02-15 0:00 ` Gautier
1999-02-16 0:00 ` Ken Thomas
1999-02-17 0:00 ` Nick Roberts
1999-02-18 0:00 ` robert_dewar
1999-02-18 0:00 ` Nick Roberts
1999-02-18 0:00 ` robert_dewar
1999-02-19 0:00 ` Nick Roberts
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` dennison
1999-02-19 0:00 ` William Clodius
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` Nick Roberts
1999-02-20 0:00 ` robert_dewar
1999-02-22 0:00 ` Nick Roberts
1999-02-19 0:00 ` Phillip Helbig
1999-02-19 0:00 ` William Clodius
1999-02-19 0:00 ` Nick Roberts
1999-02-20 0:00 ` robert_dewar
1999-02-22 0:00 ` Nick Roberts
1999-02-23 0:00 ` Robert I. Eachus
1999-02-24 0:00 ` White rabbit (was: should I be interested in ada?) dennison
1999-02-25 0:00 ` Alice books " JP Thornley
1999-02-25 0:00 ` Robert I. Eachus
1999-02-22 0:00 ` should I be interested in ada? dennison
1999-02-20 0:00 ` robert_dewar
1999-02-20 0:00 ` Steve Doiel
1999-02-18 0:00 ` Jerry Petrey
1999-02-18 0:00 ` Nick Roberts
1999-02-18 0:00 ` Dan Nagle
1999-02-18 0:00 ` nabbasi
1999-02-19 0:00 ` Nick Roberts
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` Nick Roberts
1999-02-19 0:00 ` William Clodius
1999-02-20 0:00 ` Nick Roberts
1999-02-21 0:00 ` robert_dewar
1999-02-21 0:00 ` William Clodius
1999-02-22 0:00 ` Nick Roberts
1999-02-19 0:00 ` robert_dewar
1999-02-21 0:00 ` William Clodius
1999-02-23 0:00 ` Robert I. Eachus
1999-02-19 0:00 ` Dan Nagle
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` Dan Nagle
1999-02-19 0:00 ` Nick Roberts
1999-02-23 0:00 ` Peter Hermann
1999-02-18 0:00 ` Joel Seidman
1999-02-18 0:00 ` fraser
1999-02-19 0:00 ` Matthew Heaney
1999-02-20 0:00 ` fraser
1999-02-18 0:00 ` William Clodius
1999-02-18 0:00 ` robert_dewar
1999-02-19 0:00 ` William Clodius
1999-02-19 0:00 ` Nick Roberts
1999-02-20 0:00 ` robert_dewar [this message]
1999-02-22 0:00 ` Nick Roberts
1999-02-22 0:00 ` William Clodius
1999-02-23 0:00 ` robert_dewar
1999-02-23 0:00 ` Nick Roberts
1999-02-22 0:00 ` William Clodius
1999-02-23 0:00 ` Nick Roberts
1999-02-23 0:00 ` William Clodius
1999-02-25 0:00 ` Nick Roberts
1999-02-25 0:00 ` robert_dewar
1999-02-23 0:00 ` Robert I. Eachus
1999-02-24 0:00 ` William Clodius
1999-02-24 0:00 ` Nick Roberts
1999-02-26 0:00 ` Robert A Duff
1999-02-27 0:00 ` Semantic info pragmas (was: should I be interested in ada?) Nick Roberts
1999-03-01 0:00 ` Samuel Tardieu
1999-03-01 0:00 ` Robert A Duff
1999-02-24 0:00 ` should I be interested in ada? William Clodius
1999-02-25 0:00 ` Nick Roberts
1999-02-25 0:00 ` robert_dewar
1999-02-26 0:00 ` Nick Roberts
1999-02-18 0:00 ` nabbasi
1999-02-18 0:00 ` robert_dewar
1999-02-18 0:00 ` robert_dewar
1999-02-18 0:00 ` Nick Roberts
1999-02-18 0:00 ` William Clodius
1999-02-18 0:00 ` dennison
1999-02-20 0:00 ` Hartmut H. Schaefer
1999-02-20 0:00 ` bill
1999-02-21 0:00 ` dewar
1999-02-21 0:00 ` dewar
1999-02-22 0:00 ` dennison
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