Re: Memory limits in Ada where Fortran has none

[Craig Carey <research@ijs.co.nz>]

On Wed, 09 Mar 2005 16:39:34 +1300, Craig Carey wrote:
>On Tue, 08 Mar 2005 11:24:42 GMT, "Dr. Adrian Wrigley" wrote:
>>On Sun, 06 Mar 2005 19:05:21 -0500, Robert A Duff wrote:
>...
>>I am very wary of a test like this because GNAT sometimes
>>silently accesses the wrong element of very large data, if I
>>remember correctly. A correctly written program can (and did!)
>>thus fail catastrophically.  Large records in particular are
>>suspect (on GNAT 3.15p, x86). (I have no test case to hand
>...
>

There is the Prime95 Torture Test program that is very sensitive at
detecting mistakes in floating point computations:

  Prime95 v238: http://www.mersenne.org/freesoft.htm

The Tortue Test can easily find summing probems that are too small to
cause crashes of the Windows operating system. Prime95 seems to always
fail to complain about correctly running hardware.

A GNAT integer program (sorting arrays), I have, now runs 50% faster
 after I upgraded from a modern Duron 1600 to a Sempron 2400+ running
 at 2090MHz (10x multiplier).

Integer CPU computation speeds only rising by 24% (said a Sisoft Sandra
program http://www.sisoftware.co.uk/). Raising the voltage from 1.6V to
1.775V gave about 6% extra speed to the integer memory bandwidth speed.

Apparently my GNAT Windows program is limited by the Integer memory
bandwidth or the FSB or whatever, since the Intger memory bandwidth
rose by 55% and Integer CPU speeds ultimately by 33-34%.

>It might be a bug in the memory paging code. What's the OS ?.

It seems to be Linux since the e-mail came from:
  slinuxchip.demon.co.uk.uk.uk>

Of course, a compiler that can't add seems improbable.
I thought the silence about Linux bugs might be due some comment, but
perhaps the most likely thing is that the OS is concealing that the
hardware can't add properly.