Re: gcc 3.2 makes slower code

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Article #424

#424

From: Wit Jakuczun
Date: Mon, 25 Nov 2002 20:48

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On Mon, 25 Nov 2002 19:01:55 GMT, 
Jeffrey Cunningham <jeffrey@cunningham.net> wrote:

> conclusions: (1) it isn't the I/O. The "slowdown factor" going to gcc 3.2
> is x1.6 with I/O and x1.5 without. 
Try this code:

   #include <fstream>
   int main() {
      std::ofstream out("out.txt");

      for(int i=0;i<1000000;++i)
         out << i << '\n'; //compare with endl
   };

If there is only 1.5-1.6 slow down beetwen 3.2 and 2.95 then it will
mean that I have problems with my compiler.
How did you compile your 3.2 version and what is your Linux
(distribution)?

> [..] And (2) it makes no difference to these
> calculations (intensive floating point vector operations) whether I use
> -O3 or -O2. 
It doesn't have to. I think you should rather use some math
optimizations (for example sse or mmx).

-- 
Wit Jakuczun                                                   
mailto:wj178839@wp.pl

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From: Wit Jakuczun <wit@wp.pl>
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Subject: Re: gcc 3.2 makes slower code
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Date: Mon, 25 Nov 2002 21:48:10 +0100
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