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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