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From: dennison@romulus23.DAB.GE.COM (Ted Dennison)
Newsgroups: comp.lang.ada
Subject: Re: Government Policy on Ada Acquisitions
Date: 9 Sep 1994 14:08:49 GMT
Organization: General Electric SCSD, Daytona Beach FL
Sender: dennison@romulus23 (Ted Dennison)
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References: <aetechca.3.000FE9D9@powergrid.electriciti.com>
 <1994Sep7.155252.14027@ocsystems.com> <34n3mk$3c8@theopolis.orl.mmc.com>
 <34nmfo$mpi@jac.zko.dec.com>
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Date: 1994-09-09T14:08:49+00:00
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In article <34nmfo$mpi@jac.zko.dec.com>, brett@ada9x.enet.dec.com (Bevin R. Brett) writes:
|> 
|> In article <34n3mk$3c8@theopolis.orl.mmc.com>, dennison@romulus23.DAB.GE.COM (Ted Dennison) writes...
|> 
|> >I wouldn't worry too much. I implemented a program in Sun (Verdix) Ada 
|> >and then translated it to GNAT (our customer site has no liscence for
|> >Sun Ada). GNAT's executable ran about %20 slower.
|> ...
|> >For you legal types, the program made heavy use of floating-point 
|> >math and very heavy use of disk I/O. Neither executable was compiled
|> >with optimizations.
|> 
|> 
|> It is REALLY SILLY to compare the execution times produced by two different
|> compilers for the same platform WITHOUT TURNING ON THE OPTIMISER!
|> 
|> Such poor benchmarking techniques, followed by the wide dissemination of the
|> results, are a major source of false information in the computer business.  It
|> is being practised by individuals, companies, and even trade magazines; and all
|> it does is cause totally bogus impressions of machines, languages, and compilers
|> to become "common knowlege".
|> 

Well, Bevin it could have been worse; I could have left out that information
altogether. I purposely mentioned the level of optimization I used so that
those more knowlegeable than I (and you CERTAINLY qualify) would be able 
to judge the validity of these figures. 

However, since GNAT is still unfinished, wouldn't it be MORE unfair to compare
its optimized code to the code produced by a commercial compiler that has fully
matured optimization capabilities? Perhaps someone associted with the GNAT project
could correct me on this point if I'm wrong. I'm sure you are absolutely correct
as far as comparing two COMMERCIAL compilers.

A far bigger problem with my numbers is that they are just ONE data point. There
is no evidence that a different application might not run 20% faster compiled 
under GNAT. 

I suspect the IO packages I used are the main speed culprit, not the compiler
optimizations. The Sun Ada IO packages appear to be much more complicated 
and low-level than the ones I used under GNAT.

T.E.D.