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From: "Clifford J. Nelson" <cnelson9@gte.net>
Subject: Ada95 speed
Date: 1999/05/18
Message-ID: <3740C535.7C6200A8@gte.net>#1/1
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NNTP-Posting-Date: Tue, 18 May 1999 00:47:22 GMT
Newsgroups: comp.lang.ada
Date: 1999-05-18T00:00:00+00:00
List-Id: <comp.lang.ada>

Ten years ago a Mandelbrot set computation and display on a 1200x700
screen with eight bit color took six seconds in C on a MacIIfx.

The following computations (leaving out all the with statements that you
need for the Mac) take ten seconds on an iMac 266 MHertz Mac OS 8.5.1
with the CodeBuilder Ada95 GNU from Tenon. I think it should run ten
times faster.

Is Ada95 slow in order to be safe?
Is GNU Ada95 slower than most Adas?
Is the iMac slow? Mac OS 8.5.1 slow?  CodeBuilder?
Why does it take so long?

Program follows--------

with Ada.Numerics.Complex_Types;
use Ada.Numerics.Complex_Types;

procedure Mandel is

-- Initialize procedure goes here for windRect.bottom and windRect.top

procedure Display(Mag : in Float) is
    It : Integer;
    X, Y : Float;
    C, Z : Complex;
    Num_Iters : constant := 64;
    Vertical_Maximum : constant Short_Integer := windRect.bottom;
    Horizontal_Maximum : constant Short_Integer := windRect.Right;
    Ver_Size : constant Float := Float(Vertical_Maximum + 1);
    Hor_Size : constant Float := Float(Horizontal_Maximum + 1);
    StartY : constant Float := -Mag * Ver_Size;
    StartX : constant Float := -Mag * Hor_Size;
    Step : constant Float :=  2.0 * Mag ;

  begin
   Y := StartY;
   for Y_Pos in windRect.top..windrect.bottom - 1 loop
      X := StartX;
      for X_Pos in windRect.left..windRect.right loop
        Z := (X, Y); -- Complex value; standard Ada 95!
        C := Z;
        for I in 0..Num_Iters loop
          It := I;
          exit when (abs( Z)) > 2.0;
          Z := Z * Z + C; -- Complex arithmetic
        end loop;
    -- draw pixel here in color depending on variable It.
    X := X + Step;
    end loop;
   Y := Y + Step;
   end loop;
  end Display;

begin -- Main body of program Mandel
  Initialize;
   Display(0.0025); -- draw the fractal!
  loop
    exit when Events.Button;
  end loop;
end Mandel;