Re: [Haskell-beginners] Performance of Idiomatic lazy Haskell

1 Feb 2010

      Daniel, here another feedback:

F:\MeineUebungen>ghc -O2 -fexcess-precision -fvia-C -optc-O3 -o luaLoop --make p
085-pi_lualoop.hs
[1 of 1] Compiling Main             ( p085-pi_lualoop.hs, p085-pi_lualoop.o )
Linking luaLoop.exe ...

F:\MeineUebungen>echo '0.00000001' | time ./luaLoop
Eingegebene Zeit kann nicht übernommen werden.
Geben Sie die neue Zeit ein:

F:\MeineUebungen>luaLoop +RTS -sstderr -RTS
luaLoop +RTS -sstderr
EPS:
0.00000001
3.1415926485894725
          61,428 bytes allocated in the heap
           1,316 bytes copied during GC
           4,564 bytes maximum residency (1 sample(s))
          11,820 bytes maximum slop
               1 MB total memory in use (0 MB lost due to fragmentation)

  Generation 0:     0 collections,     0 parallel,  0.00s,  0.00s elapsed
  Generation 1:     1 collections,     0 parallel,  0.00s,  0.00s elapsed

  INIT  time    0.02s  (  0.00s elapsed)
  MUT   time    8.06s  ( 16.83s elapsed)
  GC    time    0.00s  (  0.00s elapsed)
  EXIT  time    0.00s  (  0.00s elapsed)
  Total time    8.08s  ( 16.83s elapsed)

  %GC time       0.0%  (0.0% elapsed)

  Alloc rate    7,604 bytes per MUT second

  Productivity  99.8% of total user, 47.9% of total elapsed

-- Markus

On Mon, Feb 1, 2010 at 3:08 PM, Markus Böhm  wrote:
...
Daniel, I use GHC 6.12.1 and Windows XP. The time command doesn't seem
to work. It says in German: specified time can't be read. Give a new
time.
-- Markus
On Mon, Feb 1, 2010 at 2:52 PM, Daniel Fischer  wrote:
...
Am Montag 01 Februar 2010 14:31:40 schrieb Markus Böhm:
...
Daniel, with LuaJIT it needs 1.45 sec cpu-time on my machine with
attached variant.
That's pretty fast.
...
I compiled all our Haskell variants with ghc --make -O2.
Well, GHC isn't as good at loop-optimising as gcc is. Depending on the
loop, the via-C compiled binaries are between 1.4 and 2.3 times faster than
the NCG compiled.
...
I don't know about -fvia-C, have to find out. I hope I didn't
distract You with my Lua variant.
No sweat.
...
In any case thank You very much for
your advice. Markus.
You're welcome.
Can you try the below with
ghc -O2 -fexcess-precision -fvia-C -optc-O3 -o luaLoop --make Whatever.hs
and run with
echo '0.00000001' | time ./luaLoop
?
It's a fairly direct translation of the Lua code, and it runs here more or
less equally fast as (gcc compiled) C-loops.
=================================
module Main (main) where
main :: IO ()
main = do
   putStrLn "EPS:"
   eps <- readLn :: IO Double
   print $ 4*calcPi eps
calcPi :: Double -> Double
calcPi eps = go False 1 3
     where
       go bl p1 i
           | 4*abs(p2-p1) < eps    = p1
           | otherwise             = go (not bl) p2 (i+2)
             where
               p2  | bl        = p1+1/i
                   | otherwise = p1-1/i
==================================