ghc and signal processing

[Jeremy Shaw]

Hrm,

Okay, it seems that my problems maybe be due to using ghc 6.3.

Here are the results of running test under different compiler versions
(see end of message for code):


Athlon 600MHz + FreeBSD + GHC 6.0.1

real    0m0.414s
user    0m0.361s
sys     0m0.016s

Athlon 600MHz + FreeBSD + GHC 6.3 (built from CVS HEAD on Feb 15, 2004)

real    0m2.517s
user    0m2.289s
sys     0m0.069s

Pentium III 1.13GHz + Debian + GHC 6.2

real    0m0.305s
user    0m0.196s
sys     0m0.027s

Pentium III 1.13GHz + Debian + GHC 6.3 (built from CVS HEAD on Feb 1, 2004)


real    0m1.302s
user    0m1.196s
sys     0m0.044s


So it seems like maybe GHC 6.3's performance for this particular test
is around 3-5 slower?

Jeremy Shaw.


module Main where

import Data.Array
import Data.Array.IO

import System.IO

main = do h <- openFile "test.b" WriteMode
	  a <- newArray_ (1,1800000)
	  b <- mapArray id a
	  c <- mapArray id b
	  hPutArray h c 1800000


At Mon, 23 Feb 2004 13:37:45 -0800,
Mike Gunter wrote:
> 
> 
> Hmmm.  With -O2 on GHC 6.2, I get 0.177s, 0.217s, and 0.348s for your
> three Haskell examples and 0.187s (with gcc -O2) for your C example.
> The output of -ddump-simpl for the looks perfect for the second
> Haskell example.  My GHC seems to be doing a bang-up job here.  What's
> wrong with yours?  (For the third example GHC's code could be improved
> by additional inlining or hoisting of a constant array outside of the
> loop.)
> 
> 	mike
>