Re: efficient vector/matrix operations in Fortran, was Re: ... in Ada

[lutz@iks-jena.de (Lutz Donnerhacke)]

* Gautier Write-only-address wrote:
>and return the variable. Maybe a pragma Inline and a strong
>optimization can do the job on some compilers. It would be
>interesting to see if at least one is able to suppress the
>local variable in an inlined call. If not, there is no chance
>that a user-defined "+" is as efficient as a user-defined "+=".

GNAT does a pretty bad job on this subject. Using the "+=" Procedure is
works considerably better. Please play around with compiler flags.

OTOH it is possible to enhance the Kernel Interface vastly if you are
switching to direct syscalls (using System.Machine_Code). Inlining does a
pretty good job on this subject:

\f
with Kernel.Calls;
use Kernel.Calls;

procedure test_kernel is
   res : long := sys_kill (0, 0);
begin
   null;
end test_kernel;
\f
_ada_test_kernel:
	movb $37,%al
	xorl %ebx,%ebx
	movl %ebx,%ecx
	int $0x80
	ret
\f
with Ada.Text_IO;

procedure t is
   type Vector is array (Positive range <>) of Integer;

   function "+" (a, b : Vector) return Vector is
      c : Vector(a'Range);
   begin
      for i in a'Range loop
         c(i) := a(i) + b(i);
      end loop;
      return c;
   end "+";

   procedure Add_To (a : in out Vector; b : in Vector) is
   begin
      for i in a'Range loop
         a(i) := a(i) + b(i);
      end loop;
   end Add_To;
   pragma Inline("+", Add_To);
   
   procedure Print (a : in Vector) is
      package IIO is new Ada.Text_IO.Integer_IO (Integer);
      use IIO, Ada.Text_IO;
   begin   
      for i in a'Range loop
         Put (i);
         Put (a (i));
      end loop;
      New_Line;
   end Print;
   
   a : Vector(1..3) := (others => 3);
   b : Vector(1..3) := (1, 2, 3);
   c : Vector(1..3) := (4, 5, 6);
   d : Vector(1..3);
begin
   d := a + b + c;
   Print(d);
   d := a; Add_To (d, b); Add_To (d, c);
   Print(d);
end t;