From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,1d575f572a099528
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2001-12-07 10:53:52 PST
Newsgroups: comp.lang.ada
Path: 
 archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!out.nntp.be!propagator-SanJose!in.nntp.be!news-out.visi.com!hermes.visi.com!uunet!ash.uu.net!xyzzy!nntp
From: Jeffrey Carter <jeffrey.carter@boeing.com>
Subject: Re: What is faster Ada or C?
X-Nntp-Posting-Host: e246420.msc.az.boeing.com
Content-Type: text/plain; charset=us-ascii
Message-ID: <3C110823.4BC6FF07@boeing.com>
Sender: nntp@news.boeing.com (Boeing NNTP News Access)
Content-Transfer-Encoding: 7bit
Organization: The Boeing Company
X-Accept-Language: en
References: <3c08314d$0$158$9b622d9e@news.freenet.de>
 <a8MO7.46831$xS6.76121@www.newsranger.com> <3C0BA624.7A12BFA1@boeing.com>
 <3C10C26B.AA451459@nbi.dk>
Mime-Version: 1.0
Date: Fri, 7 Dec 2001 18:19:15 GMT
X-Mailer: Mozilla 4.73 [en]C-CCK-MCD Boeing Kit  (WinNT; U)
Xref: archiver1.google.com comp.lang.ada:17604
Date: 2001-12-07T18:19:15+00:00
List-Id: <comp.lang.ada>

Jacob Sparre Andersen wrote:
>  * Why are the two programs below not equivalent?
>  * How can I get the Ada program to run as fast as the C++
> program?
> 
> 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;
> };

Turn off runtime checks in Ada, or add them to the C++.

Ada's Sqrt is pickier than C/++'s; use the C sqrt from Ada.

C++'s for is really a while preceded by an assignment with an increment
added at the end; use the same structure in Ada.

Make C++ output "X = ", too.

-- 
Jeffrey Carter