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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: CRC in Ada?
Date: 1997/03/11
Message-ID: <dewar.858096758@merv>#1/1
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References: <1997Mar2.220652@nova.wright.edu> <oslo83b70l.fsf@ted.vigra.com>
 	<331d3cf9.1190126@news.logica.co.uk> <1997Mar5.083233.1@eisner>
 	<E6Kxux.FL9@world.std.com> <1997Mar5.131846.1@eisner>
 	<5fmo1k$adm@mulga.cs.mu.OZ.AU> <dewar.857693222@merv>
 <OHK.97Mar7091019@edeber.tfdt-o.nta.no> <dewar.857750112@merv>
 <3324A613.812@netcom.com>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-03-11T00:00:00+00:00
List-Id: <comp.lang.ada>


Jim Balter quoted me and replied

<<These measurements are totally misleading, and their use and
interpretation show a total *lack* of experience.  If the tests are
coded properly so that the buffer accesses aren't optimized out of
existence, you will see about a 3:1 difference in user cpu time between
the getchar version and the read version, solely as a consequence of the
getchar macro requiring more instructions.  Exactly the same number of
system calls are made, as anyone who attempts to *understand* the
issue instead of indulging in silly sophistry will know.  If you then
do, say, 20 instructions worth of processing per character, the ratio
is 23:21.  *Big* difference, like you'd expect.  Feh.>>

Well if there is one thing I am certainly not guilty of, it is lack of
experience :-)

But actually Jim, you have your quotes confused. I never said there
were a different number of systems calls, of course not! I said exactly
the opposite.

I am not quite sure what you mean by the measurements being misleading,
they are measuring exactly what they purport to be measuring. It is
possible to draw incorrect conclusions from these measurements, but
they only mislead those who wish to be mislead!