IndexScalar does not produce the correct value when it is used in the default value expression of scan and fold

[seanl]

IndexScalar does not produce the correct value when it is used in the default value expressions of scan and fold.

For example,

foo :: Vector Word32 -> Acc (Vector Word32)
foo xs
  = let
      xs' = use xs
    in
    Prelude.fst $ Acc.scanl const (xs' Acc.! constant 4) xs'

main :: IO ()
main = do
  let input = fromList 10 [0..] :: Vector (Word32)
  r <- CUDA.run $ foo input2
  putStrLn $ show r

is meant to produce

Array 10 [4,4,4,4,4,4,4,4,4,4]

but it produces

Array 10 [0,0,0,0,0,0,0,0,0,0]

[seanl]

Fixed it by replacing

f_arr <- liftFun f env

in the dispatch function for scan and fold

with

f_arr <- (++) <$> liftExp x env <*> liftFun f env

to lift the free array variables from both the default value expression and the scalar function.

Also, I added

release f_arr

at the end of dispatchScan to make sure that the device memory allocated for the free array variable.

[seanl]

Also, I added

release f_arr

at the end of dispatchScan to make sure that the device memory allocated for the free array variables is freed.

[tmcdonell]

Mon Aug  9 22:56:43 EST 2010  seanl@cse.unsw.edu.au
  * fix for the problem that IndexScalar does not produce the correct value when it is used in the default value expression of scan and fold.