Hi Manuel, thanks for your quick response.
Hi Fabian,
I've just begun to play with Data Parallel Haskell but instantly ran into a problem. My very stupid but very simple example ought to sum the values of all Nodes in a Tree. The non-vectorised code behaves like I expected, the vectorised code doesn't terminate. I compiled and ran it the same way as the example in the tutorial:
ghc -c -O -fdph-par Main.hs ghc -c -Odph -fcpr-off -fdph-par MinimalParTree.hs ghc -o MinimalParTree -fdph-par -threaded MinimalParTree.o Main.o ./MinimalParTree
My question is: Is this a bug or is something wrong with the program?
This appears to be a bug in the DPH libraries. Can you please file a bug report at http://hackage.haskell.org/trac/ghc?
An bug report is filed.
For the time being, you can change sumTree as follows to get your
program working:
sumTree :: Tree Int -> Int sumTree (Node x ns)
| lengthP ns == 0 = x | otherwise = x + sumP (mapP sumTree ns)
Unfortunately this workaround only leads to another problem. Instead of a non terminating program I now get a vectorisation error:
ghc -c -fcpr-off -fdph-par MinimalParTree.hs *** Vectorisation error *** Variable not vectorised: Control.Exception.Base.patError
Is there another workaround for that one? Thanks Fabian
-------------------------------------------------------------------- module Main where
import MinimalParTree
main = do print $ sumTreeWrapper 20
-------------------------------------------------------------------- {-# LANGUAGE PArr, ParallelListComp #-} {-# OPTIONS -fvectorise #-}
module MinimalParTree (sumTreeWrapper) where
import qualified Prelude import Data.Array.Parallel.Prelude import Data.Array.Parallel.Prelude.Int
data Tree a = Node a [: Tree a :]
testTree :: Int -> Tree Int testTree elem = Node elem emptyP
sumTree :: Tree Int -> Int sumTree (Node x ns) = x + sumP (mapP sumTree ns)
{-# NOINLINE sumTreeWrapper #-} sumTreeWrapper :: Int -> Int sumTreeWrapper elem = sumTree (testTree elem)
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