GHC Optimization: Collatz conjecture

Question

I\'ve written code for the Project Euler\'s Challenge 14, in both Haskell and C++ (ideone links). They both remember any calculations they have previously done in an array.

Answer 1

The ideone site is using a ghc 6.8.2, which is getting pretty old. On ghc version 7.4.1, the difference is much smaller.

With ghc:

$ ghc -O2 euler14.hs && time ./euler14
(837799,329)
./euler14  0.63s user 0.04s system 98% cpu 0.685 total

With g++ 4.7.0:

$ g++ --std=c++0x -O3 euler14.cpp && time ./a.out
8400511 429
./a.out  0.24s user 0.01s system 99% cpu 0.252 total

For me, the ghc version is only 2.7 times slower than the c++ version. Also, the two programs aren't giving the same result... (not a good sign, especially for benchmarking)