3 Feb
2008
3 Feb
'08
3:15 p.m.
haskell:
I can confirm this performance bug with GHC version 6.6.1 on OS X PCC (G4) Leopard.
It performs correctly, lazily keeping 'primes' for all 4 repetitions, when using "ghc -Onot" but the the doSlow fails to retain 'primes' when compiling with "ghc -O" and "ghc -O2"
Sounds like the known issue of the simplifier eta-expanding `State#` lambdas on purpose, which is good for IO, but risks re-computation. The 'calendar' nofib program exhibits this, iirc. See, http://hackage.haskell.org/trac/ghc/ticket/1168 http://hackage.haskell.org/trac/ghc/ticket/1957 Try compiling with: -fno-state-hack -- Don