[Haskell-cafe] Bug in parallel GHC runtime?

[Don Stewart]

Hi,

Thanks for the bug report.
This should be filed on the GHC bug tracker,

    http://hackage.haskell.org/trac/ghc/newticket?type=bug

And I've forwarded it to the glasgow-haskell-bugs mailing list.

kolar:
> Hello all,
> 
>  The attached file was compiled by the following command:
> 
> ghc -O2 --make -threaded ltest1pl.hs -o alall
> 
> When run in a sequential mode, I get this result:
> ./alall
> Starting ...
> Lst1: 41666666650000
> Lst2: 41669166700000
> T1: 0m 1.0e-6s
> 36
> End!
> 
> 
> On the other hand, when run in a threaded mode, I get the following error:
> ./alall +RTS -N2
> Starting ...
> Lst1: 41666666650000
> Lst2: 41669166700000
> T1: 0m 0.0s
> Segmentation fault
> 
> Is it fault of the GHC runtime, or is it something on my side?
> 
> 
> My machine: uname -a
> Linux pc 2.6.24-ARCH #1 SMP PREEMPT Sun Mar 30 10:50:22 CEST 2008 x86_64 
> Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz GenuineIntel GNU/Linux
> 
> My ghc: ghc --version
> The Glorious Glasgow Haskell Compilation System, version 6.8.2
> 
> 
> Thanks and regards
>  Dusan
> 

> --import Control.Concurrent
> --import Control.Concurrent.MVar
> import System.Time
> 
> import Control.Parallel.Strategies
> 
> --import Data.List (foldl')
> import qualified Data.ByteString as B
> 
> 
> sumAllSums [] = 0
> sumAllSums l@(_:xs) = sumlist 0 l + sumAllSums xs
>   where  sumlist res [] = res	
>          sumlist sr  (v:vs) = sumlist (sr+v) vs
> 
> wlist2wbs [] = B.pack []
> wlist2wbs l@(_:_) = B.pack $ encode l
>   where
>     encode :: Integral a => [Int] -> [a]
>     encode [] = []
>     encode (x:xs) = 
>       if x==0 then 0:0:encode xs
>       else fromIntegral (x `mod` 256) : fromIntegral (x `div` 256) : encode xs
> 
> main = do
>   putStrLn $ "Starting ..."
>   let lst1 = [0..49999]
>   let lst2 = [0..50000]
>   let bs1 = wlist2wbs lst1
>   let bs2 = wlist2wbs lst2
>   tm1 <- getClockTime
>   let (v1:v2:_) = parMap rnf sumAllSums [lst1,lst2]
>   tm1' <- getClockTime
>   putStrLn ("Lst1: " ++ show v1)
>   putStrLn ("Lst2: " ++ show v2)
>   let tdiff1 = diffClockTimes tm1' tm1
>   --let tdiff2 = diffClockTimes tm2' tm2
>   putStrLn $ "T1: " ++ show (tdMin tdiff1) ++ "m " ++ show (fromIntegral(tdSec tdiff1) + fromIntegral(tdPicosec tdiff1)/1e12) ++ "s"
>   --putStrLn $ "T2: " ++ show (tdMin tdiff2) ++ "m " ++ show (fromIntegral(tdSec tdiff2) + fromIntegral(tdPicosec tdiff2)/1e12) ++ "s"
>   putStrLn $ show $ {-ibs1 +-} B.index bs1 99999 + B.index bs2 49999 {-((bs1 + fromIntegral (B.index bs2 99999)) :: Integer)-}
>   putStrLn $ "End!"
> 
> {-
> main = do
>   tm1 <- getClockTime
>   putStrLn $ "Starting ... "
>   mv1 <- newEmptyMVar
>   mv2 <- newEmptyMVar
>   t1 <- forkIO (putMVar mv1 $! sumAllSums [0..49999])
>   t2 <- forkIO (putMVar mv2 $!  sumAllSums [1..50000])
>   v1 <- takeMVar mv1
>   v2 <- takeMVar mv2
>   killThread t1
>   killThread t2
>   putStrLn $ "Result: " ++ show (v1+v2)
>   tm2 <- getClockTime
>   let tdiff = diffClockTimes tm2 tm1
>   putStrLn $ "End! " ++ show (tdMin tdiff) ++ "m " ++ show (fromIntegral(tdSec tdiff) + fromIntegral(tdPicosec tdiff)/1e12) ++ "s"
> -}
> 

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