[Haskell-beginners] Performance of Idiomatic lazy Haskell

[Daniel Fischer]

Am Montag 01 Februar 2010 10:37:41 schrieb Markus Böhm:
> Daniel, Stephen, Felipe thanks for Your answers/advice, which I
> studied this morning. Helps me a lot on my learning curve. I guess it
> takes some time to get a feeling for the performance/runtime behaviour
> of abstractions in Haskell.
>
> Just for fun and w/o knowing Lua: I translated my Haskell
> "loops-while"-version into Lua

That's not quite a translation of the loop you posted. Not really 
important, though, small difference.

> and ran on LuaJit Beta 2.0.0. Seems to
> beat our best Haskell version.

So LuaJit Beta 2.0.0 beats gcc -O3 on such a simple loop?
I'm not going to install Lua to test, but if that's really the case, I'm 
sure the folks at gnu.org would like to hear about it.
Or don't you consider -fvia-C compiled loops to be true Haskell versions?

>
> print("EPS: ")
> EPS = io.read("*number")
> pi2 = 1
> i = 3
> s = false
> repeat
>     pi1 = pi2
>     if s then
>         pi2 = pi1 + 1.0/i
>         s = false
>     else
>         pi2 = pi1 - 1.0/i
>         s = true
>     end
>     i = i+2
>
> until EPS > 4.0 * math.abs(pi2-pi1)
>
> print("PI mit EPS", EPS," = ",4*pi1," n= ",(i-3)/2)
>
>
> -- Markus