Ackermann very inefficient with Haskell/GHC

Question

I try computing Ackermann(4,1) and there\'s a big difference in performance between different languages/compilers. Below are results on my

Answer 1

This version uses some properties of the ackermann function. It's not equivalent to the other versions, but it's fast :

ackermann :: Int -> Int -> Int
ackermann 0 n = n + 1
ackermann m 0 = ackermann (m - 1) 1
ackermann 1 n = n + 2
ackermann 2 n = 2 * n + 3
ackermann 3 n = 2 ^ (n + 3) - 3
ackermann m n = ackermann (m - 1) (ackermann m (n - 1))

Edit : And this is a version with memoization , we see that it's easy to memoize a function in haskell, the only change is in the call site :

import Data.Function.Memoize

ackermann :: Integer -> Integer -> Integer
ackermann 0 n = n + 1
ackermann m 0 = ackermann (m - 1) 1
ackermann 1 n = n + 2
ackermann 2 n = 2 * n + 3
ackermann 3 n = 2 ^ (n + 3) - 3
ackermann m n = ackermann (m - 1) (ackermann m (n - 1))

main :: IO ()
main = print $ memoize2 ackermann 4 2