Re: Memory limits in Ada where Fortran has none

[Gerald.Kasner@Physik.Uni-Magdeburg.de (Gerald)]

"braver" <deliverable@gmail.com> wrote in message news:<1110070479.250902.220540@l41g2000cwc.googlegroups.com>...
> I'm interoperating with a Fortran algorithm using a very large array of
> integers:
> 
>       PARAMETER (NMAX=100000000) ! a hundred million
>       DIMENSION ND(NMAX)
> C ...
> 
> In Ada, I declared it as
> 
>    type Intarray is array (Positive range <>) of Integer;
> 
>    ND: Intarray(1..NMAX); -- (1)
> 
> -- then I get a STORAGE_ERROR right about NMAX is 2_000_000.
> 
> If I do, instead,
> 
>    type Intarray_Ptr is access Intarray;
>    ND: Intarray_Ptr;
> -- ...
>    ND := new Intarray(1..NMAX);
> 
> -- I get the STORAGE_ERROR right about NMAX=256*1024*256, which, given
> the size of Integer as 32 bits, shows the limit of the _total heap size
> in bits_ as the max 32 value.  So it leaves me with a 256 MB heap size,
> or about 67_108_864 elements -- ~2/3 of what I need.
> How do I increase the heap size, if at all possible, or the main memory
> size?
> 
> In GNU f77, the array allocates and works fine, so I thought to import
> it with pragma Import, just as I do with subroutines -- but the linkage
> name for a variable in MAIN__ is not showing in mn main.o!  Any idea
> how to link/import a GNU f77 _variable_ from GNAT?
> 
> Overall, Ada being the language for large systems, I found it
> surprising that Fortran can allocate enough arrays to fill in my
> memory, or even take up virtual memory, while Ada raises
> STORAGE_ERRORs!  I'd like to simply use (1), as in Fortran, and be done
> with it...
> 
> Cheers,
> Alexy

You should dynamically allocate the big array:

with Ada.Text_IO;
use  Ada.Text_IO;

procedure mtest is

NMAX: constant := 3_000_000;

type Intarray is array (Positive range <>) of Integer;
type Intarray_Ptr is access all Intarray;

ND: Intarray_Ptr;
s : Long_Integer;

begin

ND:=new Intarray(1..NMAX);

for i in ND'range loop
    ND(i):=1;
end loop;

s:=0;
for i in ND'range loop
s:=s+Long_Integer(ND(i));
end loop;

Put(Long_Integer'Image(s));

end mtest;
./mtest
 3000000