[Haskell-cafe] Performance question

[Thomas van Noort]

First thing I noticed, how about removing the sqrt in isInCircle:

isInCircle :: (Floating a, Ord a)  => (a,a) -> Bool
isInCircle (x,y) = x*x + y*y <= 1.0

But you can remove sqrt from the C++ implementation as well, so it only 
improves the relative performance if the C++ implementation of sqrt is 
worse than its Haskell counterpart.

Regards,
Thomas

haskell at kudling.de wrote:
> Hi,
> 
> i have compared a C++ implementation with a Haskell implementation of the Monte Carlo Pi approximation:
> 
> http://lennart.kudling.de/haskellPi/
> 
> The Haskell version is 100 times slower and i wonder whether i do something obvious wrong.
> 
> Profiling says that the majority of the time is spend in "main". But i have no idea where.
> 
> Can someone give me a hint?
> 
> Thanks,
> Lenny
> 
>                                                                individual    inherited
> COST CENTRE              MODULE                                               no.    entries  %time %alloc   %time %alloc
> 
> MAIN                     MAIN                                                   1           0   0.0    0.0   100.0  100.0
>  main                    Main                                                 254           1  88.1   90.8   100.0  100.0
>   monteCarloPi           Main                                                 255           1   0.6    1.1    11.9    9.2
>    pairs                 Main                                                 257    10000000   0.7    1.4     0.7    1.4
>    countHits             Main                                                 256    10000001   4.2    2.9    10.6    6.7
>     accumulateHit        Main                                                 258    27852236   3.0    2.3     6.4    3.8
>      isInCircle          Main                                                 259    30000000   3.3    1.5     3.3    1.5
>  CAF:lit_r1A7            Main                                                 248           1   0.0    0.0     0.0    0.0
>   isInCircle             Main                                                 260           0   0.0    0.0     0.0    0.0
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