Enabling sse2 support on pentium4 makes my fortran-program slower.

[Mikko Ranta]

Hello!

I have a fortran 77 -code which calculates three-body problem of celestial 
mechanics so it has lot's of floating point arithemtics in it. I'm using 
Mingw at Windows and g77 from the newest version 3.2.My computer is 1.8Ghz 
Pentium4.In your homepage you say that enabling sse2 support with commands 
-msse2 (or march=pentium4) and -mfpmath=sse should increase speed of 
floating point arithmetics considerably. Examining my computer with Sisoft 
Sandra's arithmetic benchmark reveals that using sse2 should increase 
floating point arithmetics over 200%. To the point. When I enable options 
mentioned earlier, my program doesn't run any faster.In fact it runs even a 
little slower. Do I make some mistake. Or is it because all SIMD features 
are not yet implemented on GCC. Pentium 4 doesn't really shine on floating 
point arithmetics without sse2(in fact by Sisoft Sandra it's slower than my 
older computer Duron 800!) so enabling full sse2 is crucial for using this 
program which can calculate orbits for weeks. Any help or suggestions would 
be highly appreciated.

Thanks in advance.
Mikko Ranta

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