On Thursday 24 December 2009 09:09:41 Tom Davie wrote:
Here's my results on a dual core running OS X:
LappyBob:~ tatd2$ time ./test +RTS -N1 -0.117109518058233
real 0m4.608s user 0m4.400s sys 0m0.189s LappyBob:~ tatd2$ time ./test +RTS -N2 -0.117109518058233
real 0m3.648s user 0m6.360s sys 0m0.220s LappyBob:~ tatd2$ time ./test +RTS -N3 -0.117109518058233
real 0m50.679s user 1m24.235s sys 0m0.620s
Here are my results on a dual quad-core: $ ghc-6.10.4 --make -O2 -threaded mergesort.hs -o mergesort [1 of 1] Compiling Main ( mergesort.hs, mergesort.o ) Linking mergesort ... jdh30@leper:~/Programs/mine/haskell/mergesort$ time ./mergesort +RTS -K100000000 +RTS -N1 -0.117109518058233 real 0m7.664s user 0m7.528s sys 0m0.136s $ time ./mergesort +RTS -K100000000 +RTS -N2 -0.117109518058233 real 0m7.224s user 0m9.773s sys 0m0.108s $ time ./mergesort +RTS -K100000000 +RTS -N3 -0.117109518058233 real 0m7.293s user 0m11.637s sys 0m0.168s $ time ./mergesort +RTS -K100000000 +RTS -N4 -0.117109518058233 real 0m7.333s user 0m12.689s sys 0m0.360s $ time ./mergesort +RTS -K100000000 +RTS -N5 -0.117109518058233 real 0m7.449s user 0m14.757s sys 0m0.548s $ time ./mergesort +RTS -K100000000 +RTS -N6 -0.117109518058233 real 0m7.043s user 0m14.985s sys 0m0.252s $ time ./mergesort +RTS -K100000000 +RTS -N7 -0.117109518058233 real 0m8.018s user 0m19.325s sys 0m1.012s $ time ./mergesort +RTS -K100000000 +RTS -N8 -0.117109518058233 real 0m55.963s user 5m55.654s sys 0m1.492s As you can see, there is still no significant speedup from parallelism. -- Dr Jon Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/?e