few more points:
- In function f2/f3 I use a local function ``go'' instead of loopM_, it
turns out that local ``go'' function is much faster than loopM_ (loopM_ is
still faster than mapM_);
- If I add a signature for loopM_ ( loopM_ :: (Int -> IO ()) -> Int -> Int
-> Int -> IO () ), then the program runs noticeable slower even profiling
is turned off;
These really looks odd to me, and I think it really makes optimization
painful.
On Fri, Jul 3, 2015 at 9:06 AM Baojun Wang
Full source code:
https://github.com/wangbj/haskell/blob/master/lcmsum.hs
I build the program with:
ghc -O2 --make -rtsopts -prof -auto-all lcmsum
and run it with:
echo -ne '5\n100\n1000\n10000\n100000\n1000000\n' | ./lcmsum +RTS -sstderr -p
I've tried use
``let !ret = (v1+(fromIntegral i) * (fromIntegral v)) in r'' instead, however it didn't make any difference per profiling. (both Array are Unboxed).
Thanks baojun
On Fri, Jul 3, 2015 at 2:50 AM Tom Ellis < tom-lists-haskell-cafe-2013@jaguarpaw.co.uk> wrote:
On Fri, Jul 03, 2015 at 08:18:55AM +0000, Baojun Wang wrote:
Consider below function:
f3 :: UArray Int Int -> IOUArray Int Int64 -> Int -> IO () f3 u r i = let !v = u ! i in go (f31 v) i i where f31 v j = readArray r j >>= \v1 -> writeArray r j (v1 + (fromIntegral i) * (fromIntegral v)) f31 :: Int -> Int -> IO () go g k s = when (k <= maxn) ( g k >> go g (s+k) s )
When call f3:
loopM_ (f3 uu res) 1 1 1000000
Could you provide complete working code (including definitions of uu and res) and I will have a go at diagnosing. (My first guess is that you need to force (v1 + (fromIntegral i) * (fromIntegral v)).)
Tom _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe