From: William Clodius <wclodius@lanl.gov>
Subject: Re: should I be interested in ada?
Date: 1999/02/23
Date: 1999-02-23T00:00:00+00:00 [thread overview]
Message-ID: <36D33B65.446B@lanl.gov> (raw)
In-Reply-To: 7av53r$goc$2@plug.news.pipex.net
Ni<snip>
> Its true that the Ada code doesn't capture the same semantics - essentially
> that no component of Object will be assigned more than once (and they can be
> assigned in any order) - but I'm not sure that this will make any difference
> in practice (for a non-parallel target).
The above "essentially" demphasizes my main point, that it also doesn't
capture the semantics that the assignment may involve only part of the
objects X and J.
>
> The Ada procedure is inlined, so the optimizer may have the opportunity to
> eliminate null operations (e.g. assignment to self). I think Temp being too
> long will often not be a problem (for a clever dataflow analysing
> optimiser). Anyway, the problem can always be got around 'by force', by
> passing one or two more parameters into the procedure.
> <snip>
Note the fact that the intended assignment may involve only part of J,
means that your code might not only be inefficient, but also incorrect.
In thinking about this further, one additional problem to me is the
decision to make this an explicit procedure. I would normally do this
only under circumstances that need not apply to this case, i.e., if I
were going to use it at multiple points in the code or if it were doing
a complicated task that is easilly summarized. Under those circumstances
I would want a well documented routine. Reorder by itself could mean the
equivalent of any of the following
FORALL (I=1:N) X(J(I)) = X(I)
FORALL (I=1:N) X(I) = X(J(I))
FORALL (I=1:N) X(21-J(I)) = X(J(I))
FORALL (I=1:N) X(J(I)) = X(21-J(I))
The isolation of the code in this way makes it more difficult to verify
that it has the semantics required in the context in which it is
currently used, and even if appropriate there, increases the chance that
it will be reused in inappropriate contexts.
--
William B. Clodius Phone: (505)-665-9370
Los Alamos Nat. Lab., NIS-2 FAX: (505)-667-3815
PO Box 1663, MS-C323 Group office: (505)-667-5776
Los Alamos, NM 87545 Email: wclodius@lanl.gov
next prev parent reply other threads:[~1999-02-23 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 ` 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 ` 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
1999-02-19 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
1999-02-18 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 ` nabbasi
1999-02-18 0:00 ` robert_dewar
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
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 [this message]
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 ` 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 ` Nick Roberts
1999-02-20 0:00 ` robert_dewar
1999-02-22 0:00 ` Nick Roberts
1999-02-19 0:00 ` William Clodius
1999-02-19 0:00 ` robert_dewar
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
1999-02-20 0:00 ` Steve Doiel
1999-02-20 0:00 ` robert_dewar
1999-02-22 0:00 ` dennison
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
1999-02-18 0:00 ` should I be interested in ada? 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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