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FORTRAN implementation in Lenny



Hello.

I'm trying to compile the file <nbody.f90> from <http://shootout.alioth.debian.org/> [The Computer Language Benchmarks Game] in a Toshiba Satellite A200-1C0 with the specifications shown below. The problem I've got is that when I compile the file with GNU FORTRAN 95 4.3.2-1-1 and G95 FORTRAN 0.91, and the options shown below, the difference in computing time between the binaries created by both compilers is huge. Does anybody know what it is so?? I thought both compilers would yield executables with 'similar results' for the elapsed time when running. I think it is very frustrating, even if we compare it to gcc, the Intel FORTRAN Compiler or the Portland Group FORTRAN.

    ]$ gcc -O3 -lm -march=nocona -o nbody.x nbody.c
    ]$ time ./-o nbody.x 50000000
         Energy 0: -0.169075164
         Energy 1: -0.169059907
         Elapsed time: 1m 17.4s

    ]$ f95 -O3 -lm -march=nocona -o nbody.x nbody.f90
    ]$ time ./nbody.x 50000000
         Energy 0: -0.169075164
         Energy 1: -0.169059907
         Elapsed time: 2m 31.7s

    ]$ g95 -O3 -lm -march=nocona -o nbody.x nbody.f90
    ]$ time ./nbody.x 50000000
         Energy 0: -0.169075164
         Energy 1: -0.169059907
         Elapsed time: 1m 40.3s

Looking forward to hearing from you, and sincerely,

Adolfo

PS. Laptop specifications:
      Processor: 2x Intel(R) Core(TM) Duo CPU T2350 @ 1.86GHz / FSB @ 800 MHz
      Memory: 2066MB (366MB used)
      Operating System: Debian GNU/Linux 5.0.3 (Kernel 2.6.26-2-686)

---
Department of Chemistry -- Surface Science Research Centre
University of Liverpool
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Liverpool, L69 7ZD
United Kingdom

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