#14727: Unboxed sum performance surprisingly poor -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Keywords: UnboxedSums | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I tried performing worker-wrapper manually on `Data.IntMap.lookup`: {{{#!hs lookup# :: Int -> IntMap a -> (# (# #) | a #) lookup# = -- The obvious modification of the current implementation lookup :: Int -> IntMap a -> Maybe a lookup k m = case lookup# k m of (# | a #) -> Just a _ -> Nothing }}} Unfortunately, the `lookup` benchmark ''slowed down''. I verified that the benchmark indeed performs an immediate case analysis on the result (with `fromMaybe`), so it ''should'' go faster. And yet it goes slower. Caveat: I have not yet gotten things set up to be able to check with 8.4, so if there have been improvements in `UnboxedSum` performance since `8.2.2`, this may all be silly. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14727 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler