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Date:	Sun, 18 Jul 2004 09:24:35 -0700
To:	"Alex Vinokur" <alexvn AT connect DOT to>, cygwin AT cygwin DOT com
From:	Tim Prince <tprince AT computer DOT org>
Subject:	Re: Performance: g++ Cygwin vs. other compilers (copying char[] to vector)
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At 08:48 AM 7/18/2004, Alex Vinokur wrote:


>"Tim Prince" <tprince AT computer DOT org> wrote in message 
>news:6 DOT 0 DOT 1 DOT 1 DOT 0 DOT 20040718063702 DOT 01f796e8 AT imap DOT myrealbox DOT com...
> > At 05:00 AM 7/18/2004, Alex Vinokur wrote:
> >
> > >Hi,
> > >
> > >How to explain so considerable difference in performance: g++ Cygwin vs.
> > >other compilers in tests below?
>[snip]
>
> > I don't find your compile options, or whether you have profiled.  For g++
> > under cygwin,
>[snip]
>
>g++ *.cpp -o cps_cyg.exe   // g++ Cygwin
>g++ -mno-cygwin *.cpp -o cps_mgw.exe  // g++ Mingw
>gpp *.cpp -o cps_dj.exe  // g++ Djgpp
>cl /EHsc *.cpp -o cps_ms.exe   // C++ Microsoft
>dmc -I. -IC:/dm/stlport/stlport -Ae *.cpp -o cps_dm.exe  // C++ Digital Mars

Microsoft C default is a good compromise between compilation speed and 
performance.  g++ Cygwin aims for compilation speed and no transformations 
which inhibit debugging.  Performance simply is not comparable without 
normal optimization:
g++ -O3 -Drestrict=__restrict__ -funroll-loops -march=pentium4 -mfpmath=sse 
*.cpp
CL /EHsc /Ox /arch:SSE2 *.cpp
I have no idea about Digital Mars, but STLport does have more optimization 
than MS.
Nor do I know if any of your versions of g++ tinker with default optimization.
I believe clock() is implemented differently between cygwin and msvcrt, and 
you may have additional variations represented here.

Tim Prince 


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