From: "Randy Brukardt" <randy@rrsoftware.com>
Subject: Re: how to copy complete column (or row) of matrix to another?
Date: Mon, 2 Oct 2017 18:08:57 -0500
Date: 2017-10-02T18:08:57-05:00 [thread overview]
Message-ID: <oqugub$iqi$1@franka.jacob-sparre.dk> (raw)
In-Reply-To: e7eb0977-c449-4d52-8010-72df7c261e0f@googlegroups.com
"Lucretia" <laguest9000@googlemail.com> wrote in message
news:e7eb0977-c449-4d52-8010-72df7c261e0f@googlegroups.com...
>I agree that multi-dimensional array slices should be supported. One
>of the tenet's of Ada is to leave the implementation of things up to the
>compiler, because it knows how best to do it, e.g. parameter passing.
>
>I asked about it here,
>https://groups.google.com/d/msg/comp.lang.ada/L9XiRrjm3B0/cXfKlQ9-AwAJ
>and the response was, it's not going to happen due to a slice being a name
>as Randy mentions,
>but it's not a request to speed up the assignment, it's just syntactic
>sugar to aid readability,
>another of Ada's tenets.
Sigh.
The problem is that supporting that would slow down ALL array assignments to
parameters, regardless of whether or not the 2-d slices are used. Every such
assignment would have to be element at a time, because there would be no way
to determine (within the subprogram) whether or not some slices were used
that makes the array non-contiguous.
It also would make array indexing operations on such parameters much more
expensive, for the same reason.
Use of matrixes is thought to be common enough that such a performance hit
(on code *not* using slices) is unacceptable. This is known as a
"distributed overhead", where the existence of a feature makes code that
doesn't use it more expensive.
Randy.
next prev parent reply other threads:[~2017-10-02 23:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-05 8:41 how to copy complete column (or row) of matrix to another? Nasser M. Abbasi
2017-09-05 22:45 ` Randy Brukardt
2017-09-05 23:10 ` Nasser M. Abbasi
2017-09-06 5:34 ` faryumg
2018-03-21 13:58 ` Marius Amado-Alves
2018-03-30 21:25 ` gerdien.de.kruyf
2017-09-06 7:17 ` Simon Wright
2017-09-06 7:31 ` Dmitry A. Kazakov
2017-09-09 22:33 ` darek
2017-09-09 22:48 ` darek
2017-09-12 12:57 ` Lucretia
2017-10-02 23:08 ` Randy Brukardt [this message]
2017-09-12 21:22 ` Johan Söderlind Åström
2017-09-17 12:01 ` Robert Eachus
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