<div dir="ltr">-- + Roman,<div><br></div><div>-- hey Roman,</div><div><br></div><div>-- 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?</div>
<div><br></div><div><br></div><div><div style="font-family:arial,sans-serif;font-size:13px">{-# LANGUAGE DeriveGeneric #-}</div><div style="font-family:arial,sans-serif;font-size:13px">import Control.DeepSeq</div><div style="font-family:arial,sans-serif;font-size:13px">
import System.IO</div><div style="font-family:arial,sans-serif;font-size:13px">import GHC.Generics (Generic)</div><div style="font-family:arial,sans-serif;font-size:13px">import qualified Data.Vector as V</div><div style="font-family:arial,sans-serif;font-size:13px">
import qualified Data.ByteString.Lazy.Char8 as BL</div><div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">scanl' :: NFData a => (a -> b -> a) -> a -> [b] -> [a]</div>
<div style="font-family:arial,sans-serif;font-size:13px">scanl' f q ls = q : (case ls of</div><div style="font-family:arial,sans-serif;font-size:13px"> [] -> []</div><div style="font-family:arial,sans-serif;font-size:13px">
x:xs -> let q' = f q x</div><div style="font-family:arial,sans-serif;font-size:13px"> in q' `deepseq` scanl' f q' xs)</div><div style="font-family:arial,sans-serif;font-size:13px">
<br></div><div style="font-family:arial,sans-serif;font-size:13px">-- this runs without blowing up</div><div style="font-family:arial,sans-serif;font-size:13px">-- main = print $ last $ scanl' (+) (0::Int) [0..]</div>
<div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">data Simple = Simple (V.Vector Double)</div><div style="font-family:arial,sans-serif;font-size:13px">
deriving (Show, Generic)</div><div style="font-family:arial,sans-serif;font-size:13px"><br></div><div style="font-family:arial,sans-serif;font-size:13px">instance NFData Simple</div><div style="font-family:arial,sans-serif;font-size:13px">
<br></div><div style="font-family:arial,sans-serif;font-size:13px">--this blows up</div><div style="font-family:arial,sans-serif;font-size:13px">main = do</div><div style="font-family:arial,sans-serif;font-size:13px"> let initial = Simple $ V.fromList (take 100 $ repeat 0)</div>
<div style="font-family:arial,sans-serif;font-size:13px"> sumvs (Simple a) (Simple b) = Simple $ V.zipWith (+) a b</div><div style="font-family:arial,sans-serif;font-size:13px"> print $ last $ scanl' sumvs initial $ repeat $ initial</div>
</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Apr 16, 2013 at 12:36 PM, anatoly yakovenko <span dir="ltr"><<a href="mailto:aeyakovenko@gmail.com" target="_blank">aeyakovenko@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">This compiles but the process runs out of memory, so it seams that NFData derivation isn't doing its job.<br>
<div class="HOEnZb"><div class="h5"><br>
<br>
On Apr 16, 2013, at 12:15 PM, José Pedro Magalhães <<a href="mailto:jpm@cs.uu.nl">jpm@cs.uu.nl</a>> wrote:<br>
<br>
> What is the error that you get?<br>
><br>
><br>
> Cheers,<br>
> Pedro<br>
><br>
> On Tue, Apr 16, 2013 at 8:07 PM, Anatoly Yakovenko <<a href="mailto:aeyakovenko@gmail.com">aeyakovenko@gmail.com</a>> wrote:<br>
> -- ok, something in deriving NFData using Generics in a type that has a Vector in it.<br>
><br>
><br>
> {-# LANGUAGE DeriveGeneric #-}<br>
> import Control.DeepSeq<br>
> import System.IO<br>
> import GHC.Generics (Generic)<br>
> import qualified Data.Vector as V<br>
> import qualified Data.ByteString.Lazy.Char8 as BL<br>
><br>
> scanl' :: NFData a => (a -> b -> a) -> a -> [b] -> [a]<br>
> scanl' f q ls = q : (case ls of<br>
> [] -> []<br>
> x:xs -> let q' = f q x<br>
> in q' `deepseq` scanl' f q' xs)<br>
><br>
> -- this runs without blowing up<br>
> -- main = print $ last $ scanl' (+) (0::Int) [0..]<br>
><br>
> data Simple = Simple (V.Vector Double)<br>
> deriving (Show, Generic)<br>
><br>
> instance NFData Simple<br>
><br>
> --this blows up<br>
> main = do<br>
> let initial = Simple $ V.fromList (take 100 $ repeat 0)<br>
> sumvs (Simple a) (Simple b) = Simple $ V.zipWith (+) a b<br>
> print $ last $ scanl' sumvs initial $ repeat $ initial<br>
><br>
><br>
><br>
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><br>
><br>
<br>
</div></div></blockquote></div><br></div>