Lennart Augustsson schrieb:
GHC doesn't normally do CSE. CSE can cause space leaks, so you can't do it willy-nilly. I'm sure there are some strict contexts where it could be done safely, but I don't think ghc uses that information (yet).
Interestingly, it can only be switched off by -fno-cse, so I suppose there should be some cases of cse. C.
On Nov 27, 2006, at 08:34 , Christian Maeder wrote:
the following code does not run as fast as expected:
modexp a e n = if e <= 0 then 1 else if even e then mod (modexp a (div e 2) n * modexp a (div e 2) n) n else mod (a * modexp a (e - 1) n) n
it gets only fast if written as:
modexp2 a e n = if e <= 0 then 1 else if even e then let d = modexp2 a (div e 2) n in mod (d * d) n else mod (a * modexp2 a (e - 1) n) n