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From: sands@clipper.ens.fr (Duncan Sands)
Subject: Re: GNAT function calling overhead
Date: 1995/04/07
Message-ID: <3m3dad$bov@nef.ens.fr>#1/1
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distribution: world
references: <3m0nv1$pv2@nef.ens.fr> <3m0psq$fl2@stout.entertain.com>
 <1995Apr6.163740@di.epfl.ch>
organization: Ecole Normale Superieure, PARIS, France
newsgroups: comp.lang.ada
Date: 1995-04-07T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <1995Apr6.163740@di.epfl.ch>, Robb.Nebbe@di.epfl.ch (Robb Nebbe) writes:
|> In article <3m0nv1$pv2@nef.ens.fr>, Duncan Sands <sands@clipper.ens.fr> wrote:
|> >PS: The corresponding C code takes about 6 seconds.  This surprises
|> >me too.
|> 
|> 
|> The main reason is most likely that the Ada code is not at all equivalent
|> to the C code.
|> 
|> If you declare
|> 
|> type Matrix is array( 0 .. 14, 0 .. 14 ) of Float;
|> 
|> and write the loops in a way that allow the compiler to optimize out
|> the bounds checks (not sure if GNAT does this) then you should get
|> the same result as with C;

Thanks for your comments.  Actually I compiled with all checking
suppressed (range checking and others) for exactly this reason.
Therefore range checking is not the culprit.  I'm not too sure what
the culprit could possibly be.  In any case, the comparison I made
with C was quick and nasty so should be taken with a pinch of salt.

Duncan Sands.