ghc and signal processing

Jeremy Shaw at
Mon Feb 23 20:03:56 EST 2004


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

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