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Mail Archives: pgcc/1998/07/13/16:03:45

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Date: Sun, 12 Jul 1998 17:38:03 +0100
To: beastium-list AT Desk DOT nl
From: Vincent Diepeveen <diep AT xs4all DOT nl>
Subject: executable speed.
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Sender: Marc Lehmann <pcg AT goof DOT com>
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Hello,

I compared speeds between compilers for my chess program at my pentium pro
200Mhz running linux.

Speed of 2.7.2 is 10% slower than msvc++
Now the weird thing: 2.8.1 is *exactly* as fast as 2.7.2, no matter what
optimizations i give it. This is weird.

I tried a bunch of different optimizations, starting with:

   -O2 -mcpu=i686 -march=i686 -fomit-frame-pointer --fastmath

Note that in chessprograms FPU isn't used at all. Just integer instructions.

Now bob hyatt advised me to use
   -O

This gave same result. No speed ups.

Then before that already Steffen A. Jacob told me to use -O6,

so next run was with 
  -O6 -mcpu=i686

This didn'thelp either. All about the same speed. Perhaps 0.0x% faster or
slower, but no more than that.

The normal -O2 also didn't give anything.

How comes gcc 2.8.1 which does allow pentium pro optimization and
instruction scheduling isn't faster than a 486 optimizing compiler?

Then i tried to install pgcc, but this compiler gives all kind of header
files errors. I installed it over 2.8.1 version pgcc-2.91.34
And it says so if i do gcc --version.

However it doesn't compile!

It forgot probably to replace the header files.

How to fix this, what do i need to ftp?

Vincent


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