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Re: gcc 3.1 slower than 2.95?
- From: Harold L Hunt <huntharo at msu dot edu>
- To: Marcus Elderic Koenig <elderic at t-online dot de>, cygwin at cygwin dot com
- Date: Mon, 17 Jun 2002 09:34:21 EDT
- Subject: Re: gcc 3.1 slower than 2.95?
Marcus,
First, this is probably way off topic for the Cygwin list. You should be
asking on the gcc lists.
However, I can make one comment. In a scientific experiment you only change
one variable each time. However, you changed two:
> -> gcc 2.95
> g++ -O2 -mcpu=pentium -Wall settest.cpp -lwinmm
>
> -> gcc 3.1
> g++ -O3 -mcpu=pentium -Wall settest.cpp -lwinmm
You changed both the compiler (from 2.95 to 3.1) and the optimization flag
(from -O2 to -O3). Don't do that. Make both tests at -O2 or -O3. The -O2
flag seems to be about as high as anyone goes without doing some extensive
analysis on their own to determine if -O3 would be of any benefit. Also, the
-O3 flag can do things that make the code size much larger which can negate
the effect of a processor cache, etc. Stick with -O2 for both tests.
Harold
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