29 Nov
2007
29 Nov
'07
5:45 a.m.
The following code is the direct translation of your Haskell code
void f(int x, intset s) { printf("%d, ", x); f (intset_elem(s, x/2) ? 3*x : x/2, intset_put(s, x)); }
No, not that easy. The Haskell code works with arbitrary precision Integer, the C code with a fixed size int. On a 32 bit machine, try to calculate a_{1805133}, which equals to 19591041024. Or a_{8392780} = 26665583616. Or a_{8500000} = 10804333. These values are calculated with the Haskell program in 370s and ~1GB memory usage. Fair enough, on the same machine a C program (*two* pages long) was able to calculate a_{23448481} = 594261577728 and a_{25000000} = 192365946 in 50s and ~1GB memory usage. /BR, Mirko Rahn