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

It seems that there is some kind of bug involved. What GHC version are you using?

With GHC 7, I get the same behavior as you do. The program consumes all available memory without producing any output.

However if I compile it with GHC 6.12.1 just with ghc --make -O2 Ack.hs, it works perfectly. It computes the result in 10.8s on my computer, while plain C version takes 7.8s.

I suggest you to report this bug on GHC web site.