Re: gnat and heap size

[Claude Marinier <claude.marinier@dreo.dnd.ca>]

The application is an electromagnetic simulation. Yes, we could use sparse
matrix techniques but part of the program requires a full matrix. Perhaps
we are hitting a low level limit (is that what Adrian is saying?).

Here is a test program.

	procedure matrix is
	type matrix is array ( integer range <>, integer range <> ) of float;
	type matrix_a is access matrix;
	A: matrix_a := New matrix( 1..9000, 1..9000 );
	i : integer;
	begin
	i := 1;
	while i <= 9000 loop
	  A(i,i) := 1.0;
	  i := i + 1;
	end loop;
	end matrix;

On Tue, 25 Sep 2001, Dr Adrian Wrigley wrote:
> Claude Marinier wrote:
> > We want to use large arrays (well, large for us: 10000 x 10000 complex
> > numbers). We are using gnat 3.13p on Solaris 7. We run out of heap (heap
> > exhausted) and have not yet found a way to increase it.

> Since Ada works in bits, the sizes can overflow (signed) 32-bit
> representation. This makes handling data in excess of 256MB tricky,
> since locations of record elements are wrong, as are size attributes
> (eg a problem in generics). I solved this by calculating the sizes of
> each element, multiplying by the number of elements, adding in each
> record component's size.  Nasty. But it was 10-100 times the speed of
> more obvious solutions.
>
> I suspect you have a 64-bit architecture, and *may* not hit the 'size
> problems I had with GNAT.  If you stick to simple arrays, you might be
> OK. I was using GNAT 3.12p on a '686 processor.

> (by the way... what do you use such large matrices for?)

-- 
Claude Marinier, Information Technology Group    claude.marinier@dreo.dnd.ca
Defence Research Establishment Ottawa (DREO)    (613) 998-4901  FAX 998-2675
3701 Carling Avenue, Ottawa, Ontario  K1A 0Z4         http://www.dreo.dnd.ca