bearophile <bearophileh...@lycos.com> writes: > This is the nbody benchmark of the Shootout site: > http://shootout.alioth.debian.org/u32/performance.php?test=nbody > > The faster version is a Fortran one, probably thanks to vector operations > that allow a better SIMD vectorization. > > This is the C++ version: > http://shootout.alioth.debian.org/u32/program.php?test=nbody&lang=gpp&id=1 > > C++ version compiled with: > g++ -Ofast -fomit-frame-pointer -march=native -mfpmath=sse -msse3 --std=c++0x > An input parameter is n= 3_000_000 (but use a larger number if therun > time is too much small, like 10 millions or more).
All timings done with gdc 0.30 using dmd 2.055 and gcc 4.6.2. I built with both D and C++ enabled so the back end would be the same. jlquinn@wyvern:~/d/tests$ ~/gcc/gdc/bin/g++ -O3 -fomit-frame-pointer -march=native -lm -mfpmath=sse -msse3 --std=c++0x nbody.cc -o nbody_c++ jlquinn@wyvern:~/d/tests$ time ./nbody_c++ 50000000 -0.169075164 -0.169059907 real 0m10.209s user 0m10.180s sys 0m0.010s > First D2 version (serial): > http://codepad.org/AdRSm2wP ~/gcc/gdc/bin/gdc -O3 -fomit-frame-pointer -march=native -mfpmath=sse -msse3 -frelease nbody.d -o nbody_d jlquinn@wyvern:~/d/tests$ time ./nbody_d 50000000 -0.169075164 -0.169059907 real 0m9.830s user 0m9.820s sys 0m0.000s jlquinn@wyvern:~/d/tests$ dmd -O -release nbody.d jlquinn@wyvern:~/d/tests$ time ./nbody_d 50000000 -0.169075164 -0.169059907 real 0m9.828s user 0m9.830s sys 0m0.000s > Second D2 version, three times slower thanks to vector ops, more similar to > the Fortran version: > http://codepad.org/7O3mz9en ~/gcc/gdc/bin/gdc -O3 -fomit-frame-pointer -march=native -mfpmath=sse -msse3 -frelease nbody2.d -o nbody2_d jlquinn@wyvern:~/d/tests$ time ./nbody2_d 50000000 -0.169075164 -0.169059907 real 0m26.805s user 0m26.760s sys 0m0.020s jlquinn@wyvern:~/d/tests$ dmd -O -release nbody2.d jlquinn@wyvern:~/d/tests$ time ./nbody2_d 50000000 -0.169075164 -0.169059907 real 0m26.777s user 0m26.760s sys 0m0.000s > Is someone willing to take two (or more) timings using LDC 2 compiler (I have > LDC1 only, beside DMD)? I'd like to know how much time it takes to run the > first D version *compared* to the C++ version :-) If you time the second D2 > version too, then it's better. > > Bye and thank you, > bearophile So, the upshot seems like DMD and GDC generate similar code for this test. And both D compilers generate slightly faster code than the C++ version, therefore the D front end is doing a slightly better optimization job, or your first version is slightly more efficient code. Jerry
