Performance problem with Euler problem and recursion on Int64 types

Question

I\'m currently learning Haskell using the project Euler problems as my playground. I was astound by how slow my Haskell programs turned out to be compared to similar program

Answer 1

I've played with the code a little and this version seems to run faster than Java version on my laptop (3.55s vs 4.63s):

{-# LANGUAGE BangPatterns #-}

arcLength :: Int->Int
arcLength n = arcLength' 0 (n-1) 0 0 where
    arcLength' :: Int -> Int -> Int -> Int -> Int
    arcLength' !x !y !norm2 !acc
        | x > y = acc
        | norm2 > 2*(n-1) = arcLength' (x - 1) (y - 1) (norm2 - 2*(x + y) + 2) acc
        | norm2 < 0 = arcLength' (succ x) y (norm2 + x*2 + 1) acc
        | otherwise = arcLength' (succ x) y (norm2 + 2*x + 1) (acc + 1)      

main = print $ arcLength (2^30)

:

$ ghc -O2 tmp1.hs -fforce-recomp
[1 of 1] Compiling Main             ( tmp1.hs, tmp1.o )
Linking tmp1 ...

$ time ./tmp1
843298604

real    0m3.553s
user    0m3.539s
sys 0m0.006s