[Haskell-cafe] Windows vs. Linux x64

[Bartosz Wójcik]

On Wednesday 26 November 2008 02:16:26 John Meacham wrote:
> On Tue, Nov 25, 2008 at 09:39:35PM +0100, Ketil Malde wrote:
> > This corresponds to my experiences - 64 bits is slower, something I've
> > ascribed to the cost of increased pointer size.
>
> ghc unfortunatly also uses 64 bit integers when in 64 bit mode, so the
> cost paid is increased due to that as well, Also since each math
> instruction needs an extra byte telling it to work on 64 bit data so the
> code is less dense.
>

I've done little exeriment to confirm this. Created simple pgm and ran it with 
+RTS -s option on couple different harware&OS configurations.


main = (putStrLn . show . head . drop 500000) prim 

divides d n = rem n d == 0

ldf' :: (Integral a) => [a] -> a -> a
ldf' (k:ks) n | divides k n = k
              | k^2 > n     = n
              | otherwise   = ldf' ks n

prim = filter (\x -> ldf' (2:prim) x == x) [3..] 

Results of experiment:

Win32 Core2Duo 1.8GHz 1GB RAM 
   17 Mb total memory in use
   MUT   time   56.97s  ( 57.02s elapsed)
   %GC time       0.5%

Win32 Core2Duo 2.2GHz 2GB RAM
  17 Mb total memory in use
  MUT   time   57.44s  ( 57.53s elapsed)
  %GC time       0.7%  (0.8% elapsed)

Win32 P4 2.8GHz 1GB RAM
   17 Mb total memory in use
   MUT   time  171.64s  (175.78s elapsed)
   %GC time       1.7%  (1.5% elapsed)

Linux64 Core2Duo 2.2GHz 2GB RAM
   41 MB total memory in use (1 MB lost due to fragmentation)
   MUT   time   68.26s  ( 68.92s elapsed)
   %GC time       0.9%  (1.1% elapsed)

Linux32 Core2Duo 2.3GHz 4GB RAM
   17 Mb total memory in use
   MUT   time   51.77s  ( 51.83s elapsed)
   %GC time       0.5%  (0.6% elapsed)

Experiment confirms your explanations. Also interesting how slow P4 is in 
comparison to C2D.

Best and thanks.
Bartek