I think it'd help you to open a Trac ticket, give a fully-reproducible test case, including instructions for how to reproduce, and say what isn't happening that should happen. What's odd is that loop_s29q looks strict in its Int arg, yet isn't unboxed. There is a way to get the strictness analysis to run twice -flate-dmd-anal. You could try that. Simon | -----Original Message----- | From: Glasgow-haskell-users [mailto:glasgow-haskell-users- | bounces@haskell.org] On Behalf Of Christian Höner zu Siederdissen | Sent: 01 February 2015 12:18 | To: Glasgow-Haskell-Users | Subject: stream fusion, concatMap, exisential seed unboxing | | Hi everybody, | | I'm playing around with concatMap in stream fusion (the vector package | to be exact). | | concatMapM :: Monad m => (a->m (Stream m b)) -> Stream m a -> Stream m | b concatMapM f (Stream ...) = ... | | I can get my concatMap to behave nicely and erase all Stream and Step | constructors but due to the existential nature of the Stream seeds, | they are re-boxed for the inner stream (which is kind-of annoying | given that the seed is immediately unboxed again ;-). seq doesn't help | here. | | Otherwise, fusion happens for streams and vectors, so that is ok. But | boxing kills performance, criterion says. | | Do we have s.th. in place that could help here? Currently I could use | the vector-concatMap which creates intermediate arrays, my version | which has boxed seeds, or hermit but that is too inconvenient for non- | ghc savy users. | | Viele Gruesse, | Christian | | | | Fusing concatMapM: | | concatMapM f (SM.Stream ostep t _) = SM.Stream step (Left t) Unknown | where step (Left t) = do r <- ostep t | case r of | SM.Done -> return $ SM.Done | SM.Skip t' -> return $ SM.Skip (Left | t') | SM.Yield a t' -> do s <- f a | return $ SM.Skip | (Right (s,t')) | step (Right (SM.Stream istep s _,t)) = do r <- istep s | case r of | SM.Done -> | return $ SM.Skip (Left t) | SM.Skip s' -> | return $ SM.Skip (Right (SM.Stream istep s' Unknown,t)) | SM.Yield x s' -> | return $ SM.Yield x (Right (SM.Stream istep s' Unknown,t)) | {-# INLINE [0] step #-} | {-# INLINE [1] concatMapM #-} | | testConcatMapM :: Int -> Int | testConcatMapM k = seq k $ U.unId | . SM.foldl' (+) 0 | . concatMap (\i -> SM.enumFromTo 5 k) | $ SM.enumFromTo 3 k | {-# NOINLINE testConcatMapM #-} | | CORE: | | testConcatMapM | testConcatMapM = | \ k_aCA -> | let! { I# ipv_s1xv ~ _ <- k_aCA } in ### inner loop | letrec { | $s$wfoldlM'_loop_s29q | $s$wfoldlM'_loop_s29q = | \ sc_s29i sc1_s29j sc2_s29k -> | ### unboxing | let! { I# x_a1LA ~ _ <- sc1_s29j } in | case tagToEnum# (<=# x_a1LA ipv_s1xv) of _ { | False -> $s$wfoldlM'_loop1_s29c sc_s29i sc2_s29k; | True -> | $s$wfoldlM'_loop_s29q | ### reboxing | (+# sc_s29i x_a1LA) (I# (+# x_a1LA 1)) sc2_s29k | }; | ### outer loop | $s$wfoldlM'_loop1_s29c | $s$wfoldlM'_loop1_s29c = | \ sc_s29a sc1_s29b -> | case tagToEnum# (<=# sc1_s29b ipv_s1xv) of _ { | False -> sc_s29a; | True -> | case tagToEnum# (<=# 5 ipv_s1xv) of _ { | False -> $s$wfoldlM'_loop1_s29c sc_s29a (+# sc1_s29b | 1); ### boxed seed (I# 6) | True -> $s$wfoldlM'_loop_s29q (+# sc_s29a 5) (I# 6) | (+# sc1_s29b 1) | } | }; } in | let! { __DEFAULT ~ ww_s20G <- $s$wfoldlM'_loop1_s29c 0 3 } in | I# ww_s20G | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users