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From: fjh@mundook.cs.mu.OZ.AU (Fergus Henderson)
Subject: Re: C's register keyword
Date: 1997/09/09
Message-ID: <5v3v3o$np5@mulga.cs.mu.OZ.AU>#1/1
X-Deja-AN: 271052814
References: <5uqhm2$t48$1@goanna.cs.rmit.edu.au>
 <EG71Ex.4D6.0.-s@inmet.camb.inmet.com> <5v1k1v$3mq6$1@prime.imagin.net>
Organization: Comp Sci, University of Melbourne
Newsgroups: comp.lang.ada
Date: 1997-09-09T00:00:00+00:00
List-Id: <comp.lang.ada>



dweller@news.imagin.net (David Weller) writes:

>C version:
>
>	for (int i = 0; i < 10000; i++)
>		for (int j = 0; j < 10000; j++)
>				/*some nontrivial statement*/
>
>Ada version:
>
>	for i in 0..9999 loop
>		for j in 0..9999 loop
>			--some nontrivial statement
>		end loop;
>	end loop;
>
>Using gcc/GNAT, you find that the Ada executable yields faster
>performance (assuming same optimization levels and identical times for
>the "some nontrivial statement".

I find that very hard to believe.
Perhaps I have misunderstood some of your assumptions.

Certainly if `i' and `j' are local (auto) variables whose
address is not taken, then gcc will (at -O1 or higher) put
them in registers, so I don't see why the Ada version would
be faster than the C version.

--
Fergus Henderson <fjh@cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh@128.250.37.3         |     -- the last words of T. S. Garp.