Am Mittwoch 13 Januar 2010 10:43:42 schrieb Heinrich Apfelmus:
I wonder whether it's really the liveness of pair in
mergeSP (a,b) pair = let sm = spMerge b (fst pair) in (a ++ fst sm, merge (snd sm) (snd pair))
that is responsible for the space leak, for chances are that Sparud's technique applies and pair is properly disposed of. Rather, it could be that we need the stronger property that forcing the second component will evaluate the first to NF.
I think that is responsible. At least that's how I understand the core: mergeSP (a,b) ~(c,d) = (a ++ bc, merge b' d) where (bc, b') = spMerge b c spMerge ... ---------------------------------------------------------------------- OldMerge.$wmergeSP :: [GHC.Types.Int] -> [GHC.Types.Int] -> ([GHC.Types.Int], [GHC.Types.Int]) -> (# [GHC.Types.Int], [GHC.Types.Int] #) GblId [Arity 3 Str: DmdType LLL] OldMerge.$wmergeSP = \ (ww_sny :: [GHC.Types.Int]) (ww1_snz :: [GHC.Types.Int]) (w_snB :: ([GHC.Types.Int], [GHC.Types.Int])) -> let { ds_so7 [ALWAYS Just D(SS)] :: ([GHC.Types.Int], [GHC.Types.Int]) LclId [Str: DmdType] ds_so7 = case w_snB of _ { (c_adj, _) -> case OldMerge.$wspMerge ww1_snz c_adj of _ { (# ww3_snH, ww4_snI #) -> (ww3_snH, ww4_snI) } } } in (# GHC.Base.++ @ GHC.Types.Int ww_sny (case ds_so7 of _ { (bc_ajQ, _) -> bc_ajQ }), case ds_so7 of _ { (_, b'_ajS) -> case w_snB of _ { (_, d_adk) -> OldMerge.merge b'_ajS d_adk } -- Here, in the second component of the result, -- we reference the entire pair to get the dorks } #) OldMerge.mergeSP :: ([GHC.Types.Int], [GHC.Types.Int]) -> ([GHC.Types.Int], [GHC.Types.Int]) -> ([GHC.Types.Int], [GHC.Types.Int]) GblId [Arity 2 Worker OldMerge.$wmergeSP Str: DmdType U(LL)Lm] OldMerge.mergeSP = __inline_me (\ (w_snw :: ([GHC.Types.Int], [GHC.Types.Int])) (w1_snB :: ([GHC.Types.Int], [GHC.Types.Int])) -> case w_snw of _ { (ww_sny, ww1_snz) -> case OldMerge.$wmergeSP ww_sny ww1_snz w1_snB of _ { (# ww3_snN, ww4_snO #) -> (ww3_snN, ww4_snO) } }) ---------------------------------------------------------------------- vs. mergeSP (a,b) ~(c,d) = (a ++ bc, m) where (bc,m) = spMerge b c d spMerge ... ---------------------------------------------------------------------- NewMerge.$wmergeSP :: [GHC.Types.Int] -> [GHC.Types.Int] -> ([GHC.Types.Int], [GHC.Types.Int]) -> (# [GHC.Types.Int], [GHC.Types.Int] #) GblId [Arity 3 Str: DmdType LLL] NewMerge.$wmergeSP = \ (ww_snB :: [GHC.Types.Int]) (ww1_snC :: [GHC.Types.Int]) (w_snE :: ([GHC.Types.Int], [GHC.Types.Int])) -> let { ds_soa [ALWAYS Just D(SS)] :: ([GHC.Types.Int], [GHC.Types.Int]) LclId [Str: DmdType] ds_soa = case w_snE of _ { (c_adj, d_adk) -> -- There's no reference to the pair after this case NewMerge.$wspMerge ww1_snC c_adj d_adk of _ { (# ww3_snK, ww4_snL #) -> (ww3_snK, ww4_snL) } } } in (# GHC.Base.++ @ GHC.Types.Int ww_snB (case ds_soa of _ { (bc_ajT, _) -> bc_ajT }), case ds_soa of _ { (_, b'_ajV) -> b'_ajV } #) NewMerge.mergeSP :: ([GHC.Types.Int], [GHC.Types.Int]) -> ([GHC.Types.Int], [GHC.Types.Int]) -> ([GHC.Types.Int], [GHC.Types.Int]) GblId [Arity 2 Worker NewMerge.$wmergeSP Str: DmdType U(LL)Lm] NewMerge.mergeSP = __inline_me (\ (w_snz :: ([GHC.Types.Int], [GHC.Types.Int])) (w1_snE :: ([GHC.Types.Int], [GHC.Types.Int])) -> case w_snz of _ { (ww_snB, ww1_snC) -> case NewMerge.$wmergeSP ww_snB ww1_snC w1_snE of _ { (# ww3_snQ, ww4_snR #) -> (ww3_snQ, ww4_snR) } }) ----------------------------------------------------------------------