#3586: Initialisation of unboxed arrays is too slow
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Reporter: simonpj | Owner:
Type: run-time performance bug | Status: new
Priority: high | Milestone: 6.12.2
Component: libraries (other) | Version: 6.10.4
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Comment (by simonpj):
Concerning int-e's patch, why do you say that
{{{
}}}
That should not happen. I've just tried it with this module:
{{{
module Seq where
import Control.Monad
import Data.Array.Base
newArrayImplSeq (l,u) initialValue
= do let n = safeRangeSize (l,u)
marr <- unsafeNewArray_ (l,u)
sequence_ [unsafeWrite marr i initialValue | i <- [0 .. n - 1]]
return marr
newArrayImplFor (l,u) initialValue
= do let n = safeRangeSize (l,u)
marr <- unsafeNewArray_ (l,u)
forM_ [0 .. n - 1] (\i -> unsafeWrite marr i initialValue)
return marr
doSeq :: Monad m => (Int -> m ()) -> Int -> m ()
doSeq f n = sequence_ [f i | i <- [1..n]]
doFor :: Monad m => (Int -> m ()) -> Int -> m ()
doFor f n = forM_ [1..n] f
}}}
Both versions yield identical code. So why do you think one is better than
t'other?
Secondly, it's absolutely true that GHC's current inlining of default
methods is flaky, but that is something I'm fixing as part of a long
running project called "the never-ending INLINE patch". When I'm done,
your work-around shouldn't be ncessary (although it's not harmful). Stay
tuned.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3586#comment:12>
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