dd8bd7d · streamly · git.iko.soy

git.iko.soy/streamly

Revert to using a separate GroupConsume state

commitdd8bd7d2759d4f8a9fbab4cbf911233600d37ca2 authorHarendra Kumar <harendra@composewell.com> dateThu 17 Dec 2020, 15:07 (6 years ago) parent6bc64a4

2 files changed+23−19

compare with master

unifiedsplit

design/optimization-guidelines.md+4 src/Streamly/Internal/Data/Stream/StreamD/Type.hs+19−19

design/optimization-guidelines.md+4

@@ -101,6 +101,10 @@ Step function of a stream or unfold:

101101 it is called. More states means more jumps and may affect code locality, and

102102 efficiency of low level code (e.g. register allocation) because of

103103 independent placement of the code blocks in different states.

104+

105+ In some cases we may have to go against the above guideline and introduce a

106+ separate state even though it is not necessary. See the GroupConsume state in

107+ foldMany for an example.

104108* Keep minimum possible data in state. More variables in state may lead

105109 to poor performance because the state may not fit into registers and the

106110 spill may cause allocations on each iteration of the loop. Mutable state

src/Streamly/Internal/Data/Stream/StreamD/Type.hs+19−19

@@ -588,6 +588,7 @@ take n (Stream step state) = n `seq` Stream step' (state, 0)

588588{-# ANN type GroupState Fuse #-}

589589data GroupState s fs b a

590590 = GroupStart s

591+ | GroupConsume s fs a

591592 | GroupBuffer s fs

592593 | GroupYield b (GroupState s fs b a)

593594 | GroupFinish

@@ -604,16 +605,17 @@ foldMany (Fold fstep initial extract) (Stream step state) =

604605 -- fs = fold state

605606 fs <- initial

606607 return $ Skip (GroupBuffer st fs)

608+ -- This state is not strictly required but it helps the compiler fuse the

609+ -- code.

610+ step' _ (GroupConsume st fs x) = do

611+ fs' <- fstep fs x

612+ case fs' of

613+ FL.Done b -> return $ Skip (GroupYield b (GroupStart st))

614+ FL.Partial ps -> return $ Skip (GroupBuffer st ps)

607615 step' gst (GroupBuffer st fs) = do

608616 r <- step (adaptState gst) st

609617 case r of

610− Yield x s -> do

611− res <- fstep fs x

612− return

613− $ Skip

614− $ case res of

615− FL.Done b -> GroupYield b (GroupStart s)

616− FL.Partial ps -> GroupBuffer s ps

618+ Yield x s -> return $ Skip $ GroupConsume s fs x

617619 Skip s -> return $ Skip (GroupBuffer s fs)

618620 Stop -> do

619621 b <- extract fs

@@ -628,26 +630,24 @@ foldMany1 (Fold fstep initial extract) (Stream step state) =

628630

629631 where

630632

631− {-# INLINE consume #-}

632− consume x s fs = do

633− res <- fstep fs x

634− return

635− $ Skip

636− $ case res of

637− FL.Done b -> GroupYield b (GroupStart s)

638− FL.Partial ps -> GroupBuffer s ps

639−

640633 {-# INLINE_LATE step' #-}

641634 step' gst (GroupStart st) = do

642635 r <- step (adaptState gst) st

643636 case r of

644− Yield x s -> initial >>= consume x s

637+ Yield x s -> do

638+ fi <- initial

639+ return $ Skip $ GroupConsume s fi x

645640 Skip s -> return $ Skip (GroupStart s)

646− Stop -> return Stop

641+ Stop -> return $ Stop

642+ step' _ (GroupConsume st fs x) = do

643+ fs' <- fstep fs x

644+ case fs' of

645+ FL.Done b -> return $ Skip (GroupYield b (GroupStart st))

646+ FL.Partial ps -> return $ Skip (GroupBuffer st ps)

647647 step' gst (GroupBuffer st fs) = do

648648 r <- step (adaptState gst) st

649649 case r of

650− Yield x s -> consume x s fs

650+ Yield x s -> return $ Skip $ GroupConsume s fs x

651651 Skip s -> return $ Skip (GroupBuffer s fs)

652652 Stop -> do

653653 b <- extract fs