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" -}