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From: Preben Randhol <randhol@pvv.org>
Subject: Re: Gnat optimizes better than gcc C?
Date: 1999/12/17
Message-ID: <m3r9gly2dt.fsf@kiuk0156.chembio.ntnu.no>#1/1
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References: <385800DC.DE033376@lisco.com> <3859a321.0@news.pacifier.com>
 <83djjr$qqo$1@nnrp1.deja.com>
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Organization: ProgramVareVerkstedet
NNTP-Posting-Date: 17 Dec 1999 16:10:01 GMT
Newsgroups: comp.lang.ada
Date: 1999-12-17T16:10:01+00:00
List-Id: <comp.lang.ada>

Ted Dennison <dennison@telepath.com> writes:

| In article <3859a321.0@news.pacifier.com>,
|   "DuckE" <nospam_steved@pacifier.com> wrote:
| > Check out "The Big Online Book of Linux Ada Programming" at
| > http://www.vaxxine.com/pegasoft/homes/kburtch.html
| 
| 
| Hmm. Section 7.4 shows an example of an algorithm coded in Ada and C
| where the optimizer can make the Ada code run twice as fast as the C. I
| knew it was theoreticaly possible for this to happen, due to the extra
| info Ada's types provide the compiler. However, I was under the
| impression that Gnat/gcc wasn't able to take advantage of this
| information. Is this right?

I do not know, but I compiled the Ada and C programs as is with -O3
for C and -O3 -gnatp for Ada this gave 23 seconds for the C program
and 28 seconds for Ada. Including pragma pack(atype) reduced the time
for the Ada program to about 7 seconds. I didn't not include any
pentium opt. flags.

But isn't it a bit dubious to use a benchmark that produces an overflow
error?

-- 
Preben Randhol -- [randhol@pvv.org] -- [http://www.pvv.org/~randhol/]     
         "Det eneste trygge stedet i verden er inne i en fortelling." 
                                                      -- Athol Fugard