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Subject: Re: What is faster Ada or C?
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From: Ole-Hjalmar Kristensen <ohk@clustra.com>
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Jacob Sparre Andersen <sparre@nbi.dk> writes:

> Jeffrey Carter wrote:
> 
> > Robert Dewar has stated here on several occasions that he has some
> > equivalent Ada and C programs that produce identical object code when
> > compiled with gcc.
> 
> Yes.
> 
> Related to that, I have two simple, apparantly equivalent
> programs written in respectively Ada and C++, where the GNU
> Ada and C++ compilers find it difficult to produce even
> roughly equivalent binary code or processing speed.
> 
>  * Why are the two programs below not equivalent?
>  * How can I get the Ada program to run as fast as the C++
> program?

It's probably not a good idea to include IO in testts like this. The
buffer strategy used by the different IO libraries may give very
different results.

> 
> Ada:
> 
> Compilation...: gnatmake sqrt_timer -O3 -gnatn
> Execution time: 3460 ms
> Source code:
> 
> with Ada.Numerics.Generic_Elementary_Functions;
> with Ada.Text_IO;
> with Interfaces.C;
> 
> procedure Sqrt_Timer is
> 
>    type Scalar is new Interfaces.C.Double;
> 
>    package Math is new
> Ada.Numerics.Generic_Elementary_Functions (Scalar);
> 
>    function Sqrt (Item : in Scalar) return Scalar renames
> Math.Sqrt;
>    pragma Inline (Sqrt);
> 
>    X : Scalar := 2.0;
> 
> begin  --  Sqrt_Timer
>    for i in 1 .. 10_000_000 loop
>       X := Sqrt (1.0 + X);
>    end loop;
> 
>    Ada.Text_IO.Put_Line ("X = " & Scalar'Image (X));
> end Sqrt_Timer;
> 
> 
> C++
> ===
> 
> Compilation...: g++ sqrt_timer.cpp -O3
> Execution time: 1460 ms
> Source code:
> 
> #include <math.h>
> #include <iostream.h>
> 
> int main (int argl,char* argv[]) {
> 
>    double x=2.0;
> 
>    for(int i=0;i<10000000;i++){
>       x=sqrt(1.0+x);
>    };
> 
>    cout << x << endl;
> };
> 
> 
> Jacob
> -- 
> SSLUG's julekalender - fra den 1. til den 24. december p�:
>                            http://www.sslug.dk/julekalender/

-- 
Kabelsalat ist gesund.

Ole-Hj. Kristensen