#4951: Performance regression 7.0.1 -> 7.0.1.20110201
---------------------------------+------------------------------------------
Reporter: simonmar | Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.0.2
Component: Compiler | Version: 7.0.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Runtime performance bug
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Submitted by Kazu Yamamoto on glasgow-haskell-users.
This program
{{{
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.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4951>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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