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From: Preben Randhol <randhol+abuse@pvv.org>
Newsgroups: comp.lang.ada
Subject: Re: What is faster Ada or C?
Date: Fri, 7 Dec 2001 16:50:19 +0000 (UTC)
Organization: Norwegian university of science and technology
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On 07 Dec 2001 17:16:18 +0200, Aaro Koskinen wrote:
> Jacob Sparre Andersen <sparre@nbi.dk> writes:
>>  * Why are the two programs below not equivalent?
>>  * How can I get the Ada program to run as fast as the C++ program?
> [..]
>> Compilation...: gnatmake sqrt_timer -O3 -gnatn
> [..]
>>    for i in 1 .. 10_000_000 loop
>>       X := Sqrt (1.0 + X);
>>    end loop;
> 
> Did you try with -gnatp?

I tried to add the -gnatp switch. I compiled the Ada programs twice with
the -O3 and -S switches. Whether I add the -gnatp switch or not I get
the exact same assambler source. Is this correct? 

I think the difference between the Ada and C++ program is the Sqrt
function. The assembler source for the ada program is about 2000 lines
while the C++ source is around 100. 

Note that the gcc compiler Ada (GNAT) uses is 2.8.1 while the g++ I
have is 2.95 and 3.0 (unfortunately not 2.8.1).

The execution time are 615ms for the 2.95 while 1041ms for 3.0.
So the gcc compiler also plays a role.

I simplified the two programs by removing sqrt (and using Float in Ada)
and then both programs run at the same speed, 66ms.

Preben
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