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Date: Wed, 13 Apr 2005 23:01:23 +0100
Subject: Re: Large arrays (again), problem case for GNAT
From: "(see below)" <yaldnif.b@blueyonder.co.uk>
Newsgroups: comp.lang.ada
Message-ID: <BE835543.C1F5E%yaldnif.b@blueyonder.co.uk>
References: <pan.2005.04.13.12.46.52.518681@linuxchip.demon.co.uk.uk.uk>
 <ltGdnU4oIZ3j5cDfRVn-qw@megapath.net>
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Date: 2005-04-13T23:01:23+01:00
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On 13/4/05 8:54 pm, in article ltGdnU4oIZ3j5cDfRVn-qw@megapath.net,
"Randy Brukardt" <randy@rrsoftware.com> wrote:

>  Text_IO.Put_Line ("Writing to all elements in loop");
>  for I in Big_T'Range loop
>     Big (I) := 0.0;
>  end loop;
> 
>  Text_IO.Put_Line ("Writing to 'Last element");
>  Big (Big_T'Last) := 0.0; -- Fails!!!!!

For better confirmation of success I changed this to:

>  Text_IO.Put_Line ("Writing to all elements in loop");
>  for I in Big_T'Range loop
>     Big (I) := Float(i);
>  end loop;
> 
>  Text_IO.Put_Line ("Reading 'Last element");
>  if Big (Big_T'Last) /= Float(Big_T'Last) then
>     Text_IO.Put_Line ("...FAILED");
>  else
>     Text_IO.Put_Line ("...OK");
>  end if;

It compiled and ran perfectly on my 640Mb Macintosh iBook,
GNAT 3.3 20040913 (GNAT for Mac OS X build 1650):

> First element attribute  1
> Last element attribute   210000000
> Address of first element is  33587200
> Address of last element is   873587196
> (Last element should be at higher address than first)
> Address of last element is  873587196
> Writing to all elements in loop
> Reading 'Last element
> ...OK

I see that Adrian is using Linux.
Is Linux not notorious for problems of this kind?

I seem to remember that it has some kind of optimistic allocator
that can grant a memory allocation request, only for it to fail
when you try to use the memory you appear to have been granted.

-- 
Bill Findlay
<surname><forename> chez blueyonder.co.uk