c2acb45 · streamly · git.iko.soy

git.iko.soy/streamly

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Make the sum fold numerically stable

c2acb45Adithya Kumar4 years ago

core/src/Streamly/Internal/Data/Fold.hs+9−2

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unifiedsplit

@@ -313,6 +313,7 @@ import qualified Data.Set as Set

313import qualified Prelude

314import qualified Streamly.Internal.Data.Array.Foreign.Mut.Type as MA

315import qualified Streamly.Internal.Data.Array.Foreign.Type as Array

316+import qualified Streamly.Internal.Data.Fold.Window as FoldW

316import qualified Streamly.Internal.Data.IsMap as IsMap

317import qualified Streamly.Internal.Data.IsMap as IsMap

317import qualified Streamly.Internal.Data.Pipe.Type as Pipe

318import qualified Streamly.Internal.Data.Pipe.Type as Pipe

318import qualified Streamly.Internal.Data.Ring.Foreign as Ring

319import qualified Streamly.Internal.Data.Ring.Foreign as Ring

@@ -336,6 +337,7 @@ import Streamly.Internal.Data.Fold.Type

336-- >>> import qualified Streamly.Data.Fold as Fold

337-- >>> import qualified Streamly.Data.Fold as Fold

337-- >>> import qualified Streamly.Internal.Data.Fold as Fold

338-- >>> import qualified Streamly.Internal.Data.Fold as Fold

338-- >>> import qualified Streamly.Internal.Data.Fold.Type as Fold

339-- >>> import qualified Streamly.Internal.Data.Fold.Type as Fold

340+-- >>> import qualified Streamly.Internal.Data.Fold.Window as FoldW

339-- >>> import qualified Streamly.Data.Array.Foreign as Array

341-- >>> import qualified Streamly.Data.Array.Foreign as Array

340-- >>> import qualified Streamly.Internal.Data.Parser as Parser

342-- >>> import qualified Streamly.Internal.Data.Parser as Parser

341-- >>> import Streamly.Internal.Data.Stream.Serial (SerialT(..))

343-- >>> import Streamly.Internal.Data.Stream.Serial (SerialT(..))

@@ -681,12 +683,17 @@ countDistinctInt = fmap (\(Tuple' _ n) -> n) $ foldl' step initial

681-- identity (@0@) when the stream is empty. Note that this is not numerically

683-- identity (@0@) when the stream is empty. Note that this is not numerically

682-- stable for floating point numbers.

684-- stable for floating point numbers.

683--

685--

686+-- >>> sum = FoldW.cumulative FoldW.sum

687+--

688+-- Same as following but numerically stable:

689+--

690+-- >>> sum = Fold.foldl' (+) 0

684−-- > sum = fmap getSum $ Fold.foldMap Sum

691+-- >>> sum = fmap Data.Monoid.getSum $ Fold.foldMap Data.Monoid.Sum

685--

692--

686-- @since 0.7.0

693-- @since 0.7.0

687{-# INLINE sum #-}

694{-# INLINE sum #-}

688sum :: (Monad m, Num a) => Fold m a a

695sum :: (Monad m, Num a) => Fold m a a

689−sum = foldl' (+) 0

696+sum = FoldW.cumulative FoldW.sum

690

697

691-- | Determine the product of all elements of a stream of numbers. Returns

698-- | Determine the product of all elements of a stream of numbers. Returns

692-- multiplicative identity (@1@) when the stream is empty. The fold terminates

699-- multiplicative identity (@1@) when the stream is empty. The fold terminates

core/src/Streamly/Internal/Data/Fold/Window.hs+1−1

@@ -61,7 +61,7 @@ import Streamly.Internal.Data.Tuple.Strict

62import Prelude hiding (length, sum, minimum, maximum)

64−import qualified Streamly.Data.Fold as Fold

64+import qualified Streamly.Internal.Data.Fold.Type as Fold

65import qualified Streamly.Internal.Data.Ring.Foreign as Ring

67-- $setup