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Optimize array indexing in delete' and deleteKeyExists #528

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Merged
sjakobi merged 1 commit into from
Oct 29, 2025
Merged

Optimize array indexing in delete' and deleteKeyExists #528

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70 changes: 35 additions & 35 deletions Data/HashMap/Internal.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -1121,15 +1121,12 @@ deleteFromSubtree h k s t@(BitmapIndexed b ary)
in if st' `ptrEq` st
then t
else case st' of
Empty | A.length ary == 1 -> Empty
| A.length ary == 2 ->
case (i, A.index ary 0, A.index ary 1) of
(0, _, l) | isLeafOrCollision l -> l
(1, l, _) | isLeafOrCollision l -> l
_ -> bIndexed
| otherwise -> bIndexed
where
bIndexed = BitmapIndexed (b .&. complement m) (A.delete ary i)
Empty | A.length ary == 2
, (# l #) <- A.index# ary (otherOfOneOrZero i)
, isLeafOrCollision l
-> l
| otherwise
-> BitmapIndexed (b .&. complement m) (A.delete ary i)
l | isLeafOrCollision l && A.length ary == 1 -> l
_ -> BitmapIndexed b (A.update ary i st')
where m = mask h s
Expand All @@ -1149,10 +1146,9 @@ deleteFromSubtree h k s t@(Full ary) =
deleteFromSubtree h k _ t@(Collision hy v)
| h == hy = case indexOf k v of
Just i
| A.length v == 2 ->
if i == 0
then Leaf h (A.index v 1)
else Leaf h (A.index v 0)
| A.length v == 2
, (# l #) <- A.index# v (otherOfOneOrZero i)
-> Leaf h l
| otherwise -> Collision h (A.delete v i)
Nothing -> t
| otherwise = t
Expand All @@ -1172,15 +1168,12 @@ deleteKeyExists !collPos0 !h0 !k0 !m0 = go collPos0 h0 k0 m0
let !st = A.index ary i
!st' = go collPos (nextSH shiftedHash) k st
in case st' of
Empty | A.length ary == 1 -> Empty
| A.length ary == 2 ->
case (i, A.index ary 0, A.index ary 1) of
(0, _, l) | isLeafOrCollision l -> l
(1, l, _) | isLeafOrCollision l -> l
_ -> bIndexed
| otherwise -> bIndexed
where
bIndexed = BitmapIndexed (b .&. complement m) (A.delete ary i)
Empty | A.length ary == 2
, (# l #) <- A.index# ary (otherOfOneOrZero i)
, isLeafOrCollision l
-> l
| otherwise
-> BitmapIndexed (b .&. complement m) (A.delete ary i)
l | isLeafOrCollision l && A.length ary == 1 -> l
_ -> BitmapIndexed b (A.update ary i st')
where m = maskSH shiftedHash
Expand All @@ -1197,9 +1190,8 @@ deleteKeyExists !collPos0 !h0 !k0 !m0 = go collPos0 h0 k0 m0
where i = indexSH shiftedHash
go collPos _shiftedHash _k (Collision h v)
| A.length v == 2
= if collPos == 0
then Leaf h (A.index v 1)
else Leaf h (A.index v 0)
, (# l #) <- A.index# v (otherOfOneOrZero collPos)
= Leaf h l
| otherwise = Collision h (A.delete v collPos)
go !_ !_ !_ Empty = Empty -- error "Internal error: deleteKeyExists empty"
{-# NOINLINE deleteKeyExists #-}
Expand Down Expand Up @@ -1818,16 +1810,12 @@ difference = go_difference 0
| otherwise =
let (# !st #) = A.index# ary1 i1
in case go_difference (nextShift s) st t2 of
Empty {- | A.length ary1 == 1 -> Empty -- Impossible! -}
| A.length ary1 == 2 ->
case (i1, A.index ary1 0, A.index ary1 1) of
(0, _, l) | isLeafOrCollision l -> l
(1, l, _) | isLeafOrCollision l -> l
_ -> bIndexed
| otherwise -> bIndexed
where
bIndexed
= BitmapIndexed (b1 .&. complement m) (A.delete ary1 i1)
Empty | A.length ary1 == 2
, (# l #) <- A.index# ary1 (otherOfOneOrZero i1)
, isLeafOrCollision l
-> l
| otherwise
-> BitmapIndexed (b1 .&. complement m) (A.delete ary1 i1)
st' | isLeafOrCollision st' && A.length ary1 == 1 -> st'
| st `ptrEq` st' -> t1
| otherwise -> BitmapIndexed b1 (A.update ary1 i1 st')
Expand Down Expand Up @@ -2639,6 +2627,18 @@ ptrEq :: a -> a -> Bool
ptrEq x y = Exts.isTrue# (Exts.reallyUnsafePtrEquality# x y ==# 1#)
{-# INLINE ptrEq #-}

------------------------------------------------------------------------
-- Array index arithmetic

-- |
-- >>> otherOfOneOrZero 0
-- 1
-- >>> otherOfOneOrZero 1
-- 0
otherOfOneOrZero :: Int -> Int
otherOfOneOrZero i = 1 - i
{-# INLINE otherOfOneOrZero #-}

------------------------------------------------------------------------
-- IsList instance
instance (Eq k, Hashable k) => Exts.IsList (HashMap k v) where
Expand Down