[Haskell-cafe] parallel strategies for foldMap?
johannes.waldmann at htwk-leipzig.de
Tue Oct 10 16:39:51 UTC 2017
I wonder if there is some accepted wisdom (and implementation)
to support parallel foldMap in some uniform way.
It should probably be tuneable for the case that mappend is
less or more expensive than the function to apply in the elements.
I can do the following, but it does not parallelize the mappends:
import qualified Data.Foldable as F
foldMapPar :: (Foldable f, Monoid b) => Int -> (a -> b) -> f a -> b
foldMapPar block f xs =
F.fold ( map f (F.toList xs) `using` parBuffer block rseq )
In my application, the Foldable thingy is an unbalanced tree.
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