Re: I wasn't expected that !
From: Bonj (a_at_b.com)
Date: 02/18/04
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Date: Wed, 18 Feb 2004 18:52:04 -0000
The compiler might even be as clever as to simply *not do* some of the
calculations at all, since it knows the variables don't get used in a
meaningful way. That's why I think as close to real world test scenarios
with genuine program output are better. So you don't really know, I mean
that might be why it showed as doing it really fast, when in fact it was
just not doing it as it knew it didn't need to.
"Marchel" <marchel@comcast.net> wrote in message
news:EcOdnWvLAp2erq3dRVn-uw@comcast.com...
> > You're doing these tests with the Standard Version? That's hardly a
> > relevant test for doing any kind of performance benchmarking, since that
> > compiler has no optimizer whatsoever, and all optimizer options
specified in
> > the IDE or command line are simply ignored.
>
> As I said, it's too bad for Microsoft. I'm not a professional programmer
and I cannot, as many engineers and scientists
> in similar to mine position, justify cost of more expensive versions of
the software. I mentioned that clearly in the
> test page.
>
> Consider this for example:
>
> (www.borland.com)
> Borland C++ Builder 6.0 (Personal) $69
> Borland C++ Builder 6.0 (Professional) $999
> Borland C++ Builder 6.0 (Enterprise) $2999
>
> (www.microsoft.com)
> Microsoft Visual C++ .NET (Standard) $109
> Microsoft Visual C++ .NET (Professional) $1079
>
> In fact you can download complete, full version of the Borland compiler
(without IDE) for free. Also you can get open
> source (gcc) C++ windows compiler freely. This make the price span even
more ridiculous. I'm refusing to buy expensive
> versions of the software for occasional programming sessions. My money
making job has nothing to do with computer
> programming.
>
> > > In you setting without -Op there must be something wrong with the
> > > clock measurement in the program. It is simply impossible on a today
> > > PC even overclocked to 4GHZ to execute 4 floating point double size
> > > additions and two floting point double size divisions 90,000,000
> > > times under 0.001 second. That would make your PC some kind of
> > > supercomputer.
> >
> > Actually, I think it means there's something wrong with the generated
code
> > with -O2 but not -Op. I haven't had a chance to really look into it -
the
> > benchmark cleary took about the same time as without -Op, so I'm
guessing
> > that the calculation of elapsed time somehow got bunged up.
>
> And that makes sense. On my Athlon XP 1800 + (similarly to your timing)
90,000,000 loops of four additions and two
> divisions took roughly 2 seconds. For the sake of simplicity assuming that
addition and division takes the same time, it
> means six general math operations per loop, which means about 540,000,000
math operations in two seconds or 270,000,000
> operations per second. Athlon XP 1800+ runs at 1533 MHz. So in fact it
made each operation in about 5.7 clock cycle
> which is pretty good. You can't massively improve this. That is why the
differences between Borland, C# and VC++ were
> not that big. All those compilers are in fact pretty good.
>
>
> >
> > -cd
>
> JM
>
>
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