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Enabling sse2 support on pentium4 makes my fortran-program slower.
- From: "Mikko Ranta" <ranta_mikko at hotmail dot com>
- To: gcc-help at gcc dot gnu dot org
- Date: Mon, 14 Oct 2002 16:21:40 +0300
- Subject: Enabling sse2 support on pentium4 makes my fortran-program slower.
- Bcc:
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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