Performance regression 7.0.1 -> 22.214.171.12410201
Submitted by Kazu Yamamoto on glasgow-haskell-users.
import System.IO n :: Int n = 10000 main :: IO () main = withFile "/dev/null" WriteMode $ \h -> hPutStr h . foldr1 (++) . replicate n . replicate n $ 'a'
runs much more slowly with the current 7.0 branch than with either 7.0.1 or HEAD.
He also reported that the program runs faster interpreted with runghc than when compiled. I think this is due to #917 (full-laziness), so that's a separate issue. THe regression reported in this ticket is in compiled performance relative to 7.0.1 and HEAD.
I don't see any obvious differences in the simplified output, so the difference could be in library code. I'm using libraries compiled with -O2 in all cases.