[Haskell-cafe] (Repa) hFlush: illegal operation

[Michael Orlitzky]

I'm using Repa to process a ton of MRI data. The basic process is,

  * Read in the data
  * Create a big 'ol data structure (grid) from it
  * Compute the output in parallel using 'traverse'
  * Write the output to file

However, during the last step, I'm getting,

  $ ./bin/spline3 +RTS -N4
  spline3: output.txt: hFlush: illegal operation (handle is closed)

Here's the entirety of my Main.hs:

> module Main
> where
>
> import Data.Array.Repa (
>   DIM3,
>   Z(..),
>   (:.)(..),
>   )
>
> import Values
> import Grid(make_grid, zoom)
>
> mri_shape :: DIM3
> mri_shape = (Z :. 256 :. 256 :. 109)
>
> main :: IO ()
> main = do
>   mridata <- read_values_3d mri_shape "./data/mridata.txt"
>   let g = make_grid 1 mridata
>   let output = zoom g 1
>   write_values_1d output "output.txt"


And the two functions used from the Values module,

> type Values1D = Array DIM1 Double
> type Values3D = Array DIM3 Double
>
> read_values_1d :: FilePath -> IO Values1D
> read_values_1d path = readVectorFromTextFile path
>
>
> read_values_3d :: DIM3 -> FilePath -> IO Values3D
> read_values_3d sh path = do
>   one_d <- read_values_1d path
>   return $ reshape sh one_d
>
>
> write_values_1d :: Values3D -> FilePath -> IO ()
> write_values_1d v3d path = do
>   let size3d = size $ extent v3d
>   let shape1d = (Z :. size3d)
>   let v1d = reshape shape1d v3d
>   writeVectorToTextFile v1d path


Am I doing something obviously wrong here? It takes about 45 minutes to
run up to the point of failure, so I haven't attempted much trial & error.

Packages:

  * ghc-7.2.1
  * repa-2.1.1.6
  * repa-io-2.1.0.1