Re: Large arrays (again), problem case for GNAT

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"(see below)" <yaldnif.b@blueyonder.co.uk> writes:

> 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.

Hmm.  If the OS allocates virtual address space for that giant array,
but doesn't allocate physical memory, or backing store, for it, then an
access to that array could allocate memory, thus causing Storage_Error.
That would be legitimate behavior on the part of the Ada compiler.
Maybe Adrian should try increasing the size of the paging file?

But there's a loop writing 0.0 over the whole thing, so I would guess
*that* would actually allocate the memory.  Also, the above doesn't
explain why the 'Address attribute returns strange results.

I'm not sure why you say "notorious".  It seems to me that
allocate-on-write is desirable.

- Bob