From: "Randy Brukardt" <randy@rrsoftware.com>
Subject: Re: Performance of element access in Vector
Date: Mon, 19 Jan 2009 20:17:12 -0600
Date: 2009-01-19T20:17:12-06:00 [thread overview]
Message-ID: <gl3c7s$m6i$1@munin.nbi.dk> (raw)
In-Reply-To: 0a8baaf0-19f7-40c0-a041-884e93fa7020@w39g2000prb.googlegroups.com
"Maciej Sobczak" <see.my.homepage@gmail.com> wrote in message
news:0a8baaf0-19f7-40c0-a041-884e93fa7020@w39g2000prb.googlegroups.com...
...
> A possible conclusion is that for small elements (simple numeric
> types, etc.) it makes sense to access elements by index, when they are
> copied from and into the container. For larger elements the benefit of
> accessing element in-place can be greater than the overhead of
> Update_Element.
Update_Element was added to handle large element types (such as other
containers) where the overhead of copying them would be prohibitive. I doubt
that it could be efficient for small objects that can cheaply be passed by
copy.
> Just to stir the discussion a bit, a straightforward implementation of
> the same test in C++ (with the same base compiler and a single -O2
> option) runs in 13s with indexed access and in 9.5s with iterators -
> both are based on the use of references, which do not exist in Ada.
> Not very easy to neglect this difference.
What happens in C++ when the element whose reference you are using is
deleted? In Ada.Containers, you'll get Program_Error if you try to do that -
not a dangling pointer and havoc.
Randy.
next prev parent reply other threads:[~2009-01-20 2:17 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-18 21:42 Performance of element access in Vector Maciej Sobczak
2009-01-19 0:03 ` george.priv
2009-01-19 3:23 ` george.priv
2009-01-19 11:25 ` Georg Bauhaus
2009-01-19 16:32 ` (see below)
2009-01-20 2:17 ` Randy Brukardt [this message]
2009-01-20 8:03 ` Maciej Sobczak
2009-01-20 8:26 ` Dmitry A. Kazakov
2009-01-20 22:07 ` george.priv
2009-01-21 8:52 ` Maciej Sobczak
2009-01-21 19:25 ` george.priv
2009-01-22 10:01 ` Georg Bauhaus
2009-01-22 12:43 ` Maciej Sobczak
2009-01-22 13:52 ` george.priv
2009-01-21 8:59 ` Dmitry A. Kazakov
2009-01-21 9:19 ` Maciej Sobczak
2009-01-21 10:19 ` Dmitry A. Kazakov
2009-01-21 13:14 ` Maciej Sobczak
2009-01-21 19:00 ` Dmitry A. Kazakov
2009-01-21 13:22 ` Georg Bauhaus
2009-01-23 14:56 ` Alex R. Mosteo
2009-01-20 23:01 ` Randy Brukardt
2009-01-21 9:15 ` Maciej Sobczak
2009-01-21 18:08 ` Georg Bauhaus
2009-01-23 14:55 ` Alex R. Mosteo
2009-01-23 17:30 ` Georg Bauhaus
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