-- + Roman,

-- hey Roman,

-- seems like i cant use deepseq or Generic derive of NFData on data types containing vectors. The following code tries to use deepseq to force evaluation of a type containing vectors, but when the code is running it seems to not work as expected (blows up in memory). any ideas?

{-# LANGUAGE DeriveGeneric #-}

import Control.DeepSeq

import System.IO

import GHC.Generics (Generic)

import qualified Data.Vector as V

import qualified Data.ByteString.Lazy.Char8 as BL

scanl' :: NFData a => (a -> b -> a) -> a -> [b] -> [a]

scanl' f q ls = q : (case ls of

[] -> []

x:xs -> let q' = f q x

in q' `deepseq` scanl' f q' xs)

-- this runs without blowing up

-- main = print $ last $ scanl' (+) (0::Int) [0..]

data Simple = Simple (V.Vector Double)

deriving (Show, Generic)

instance NFData Simple

--this blows up

main = do

let initial = Simple $ V.fromList (take 100 $ repeat 0)

sumvs (Simple a) (Simple b) = Simple $ V.zipWith (+) a b

print $ last $ scanl' sumvs initial $ repeat $ initial

On Tue, Apr 16, 2013 at 12:36 PM, anatoly yakovenko <aeyakovenko@gmail.com> wrote:

This compiles but the process runs out of memory, so it seams that NFData derivation isn't doing its job.

On Apr 16, 2013, at 12:15 PM, José Pedro Magalhães <jpm@cs.uu.nl> wrote:

> What is the error that you get?
>
>
> Cheers,
> Pedro
>
> On Tue, Apr 16, 2013 at 8:07 PM, Anatoly Yakovenko <aeyakovenko@gmail.com> wrote:
> -- ok, something in deriving NFData using Generics in a type that has a Vector in it.
>
>
> {-# LANGUAGE DeriveGeneric #-}
> import Control.DeepSeq
> import System.IO
> import GHC.Generics (Generic)
> import qualified Data.Vector as V
> import qualified Data.ByteString.Lazy.Char8 as BL
>
> scanl' :: NFData a => (a -> b -> a) -> a -> [b] -> [a]
> scanl' f q ls = q : (case ls of
> [] -> []
> x:xs -> let q' = f q x
> in q' `deepseq` scanl' f q' xs)
>
> -- this runs without blowing up
> -- main = print $ last $ scanl' (+) (0::Int) [0..]
>
> data Simple = Simple (V.Vector Double)
> deriving (Show, Generic)
>
> instance NFData Simple
>
> --this blows up
> main = do
> let initial = Simple $ V.fromList (take 100 $ repeat 0)
> sumvs (Simple a) (Simple b) = Simple $ V.zipWith (+) a b
> print $ last $ scanl' sumvs initial $ repeat $ initial
>
>
>
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