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optimize Natural/fold in the strict case #2585

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merged 9 commits into from
Jun 12, 2024
Merged

optimize Natural/fold in the strict case #2585

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e36815e
optimize Natural/fold in the strict case
winitzki May 11, 2024
89c54f7
remove tabs
winitzki May 11, 2024
7bbee59
fix syntax in do block
winitzki May 11, 2024
9dcac33
Update Normalize.hs
winitzki May 12, 2024
827fc45
adding wip code to Eval.hs
winitzki May 14, 2024
ed07195
fix code
winitzki May 14, 2024
9fae7ff
Merge branch 'main' into feature/optimize_natural_fold
winitzki May 31, 2024
33efa78
remove dummy change
winitzki May 31, 2024
be07882
Merge branch 'main' into feature/optimize_natural_fold
winitzki Jun 1, 2024
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12 changes: 8 additions & 4 deletions dhall/src/Dhall/Eval.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -122,7 +122,7 @@ instance Semigroup (VChunks a) where
VChunks xys z <> VChunks [] z' = VChunks xys (z <> z')
VChunks xys z <> VChunks ((x', y'):xys') z' = VChunks (xys ++ (z <> x', y'):xys') z'

instance Monoid (VChunks b) where
instance Monoid (VChunks a) where
mempty = VChunks [] mempty

{-| Some information is lost when `eval` converts a `Lam` or a built-in function
Expand Down Expand Up @@ -527,9 +527,13 @@ eval !env t0 =
-- following issue:
--
-- https://github.com/ghcjs/ghcjs/issues/782
let go !acc 0 = acc
go acc m = go (vApp succ acc) (m - 1)
in go zero (fromIntegral n' :: Integer)
go zero (fromIntegral n' :: Integer) where
go !acc 0 = acc
go (VNaturalLit x) m =
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Here, we detect the shortcut only when the accumulator is a Natural literal. However, we would like to detect the shortcut in all cases. I could not find any way of comparing Val values. What kind of code would need to be written here?

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Dhall.Eval.conv is what you want

case vApp succ (VNaturalLit x) of
VNaturalLit y | x == y -> VNaturalLit x
notNaturalLit -> go notNaturalLit (m - 1)
go acc m = go (vApp succ acc) (m - 1)
_ -> inert
NaturalBuild ->
VPrim $ \case
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12 changes: 10 additions & 2 deletions dhall/src/Dhall/Normalize.hs
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Expand Up @@ -211,8 +211,16 @@ normalizeWithM ctx e0 = loop (Syntax.denote e0)
strict = strictLoop (fromIntegral n0 :: Integer)
lazy = loop ( lazyLoop (fromIntegral n0 :: Integer))

strictLoop 0 = loop zero
strictLoop !n = App succ' <$> strictLoop (n - 1) >>= loop
strictLoop !n = do
z <- loop zero
strictLoopShortcut n z

strictLoopShortcut 0 !previous = pure previous
strictLoopShortcut !n !previous = do
current <- loop (App succ' previous)
if judgmentallyEqual previous current
then pure previous
else strictLoopShortcut (n - 1) current

lazyLoop 0 = zero
lazyLoop !n = App succ' (lazyLoop (n - 1))
Expand Down
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