[Haskell-beginners] Performance of Idiomatic lazy Haskell
markus.boehm at googlemail.com
Mon Feb 1 09:08:58 EST 2010
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
On Mon, Feb 1, 2010 at 2:52 PM, Daniel Fischer <daniel.is.fischer at web.de> 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
> go bl p1 i
> | 4*abs(p2-p1) < eps = p1
> | otherwise = go (not bl) p2 (i+2)
> p2 | bl = p1+1/i
> | otherwise = p1-1/i
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