#2171: Parallel program crashes
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Reporter: fed | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.8.3
Component: Runtime System | Version: 6.8.2
Severity: critical | Resolution:
Keywords: parallel, crash, race condition | Difficulty: Unknown
Testcase: | Architecture: Multiple
Os: Multiple |
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Comment (by MarcWeber):
Replying to [ticket:2171 fed]:
> I wrote a parallel program for computing prime numbers (see code below).
> Compiled it using
> ghc -threaded --make primes.hs
> Then run
> primes 200000 200010 +RTS -N2 -sstderr
> In 80% of runs the program crashes with segmentation fault message. My
operating system is Windows XP SP2. One time I saw a typical Windows red
cross dialog box with access violation report as a result of the run.
> But few times the program finished with correct result.
>
> {{{
> module Main where
>
> import System.Environment
> import Control.Parallel.Strategies
> import Data.Maybe
>
> chunkSize = 1000
> threads = 2
>
> maybePrimes :: [Maybe Integer]
> maybePrimes = Just 2 : Just 3 : Just 5 : [ if isPrime x then (Just x)
else Nothing | x <- candidates 7 11 ]
> where
> candidates a1 a2 = a1 : a2 : candidates (a1+6) (a2+6)
> isPrime x = all ((0 /=) . (x `mod`)) $ takeWhile ((x>=).(^2))
primes
>
> splitOnSubLists :: Int -> [a] -> [[a]]
> splitOnSubLists n xs =
> let
> (begin, end) = splitAt n xs
> in
> begin : splitOnSubLists n end
>
> maybePrimes2 :: [Maybe Integer]
> maybePrimes2 = concat $ parBuffer (threads-1) rnf
> $ splitOnSubLists chunkSize maybePrimes
>
> primes :: [Integer]
> primes = catMaybes maybePrimes2
>
> main = do
> args <- getArgs
>
> (first, last) <- case args of
> [] -> return (10, 19)
> (x:[]) -> return (f, f+9) where f = read x
> (x:y:_) -> return (read x, read y)
>
> let p = drop (first-1) $ take last $ zip [1..] primes in
> mapM (\(x,y) -> putStrLn (show x ++ " -> " ++ show y)) p
> }}}
I can reproduce this error as well (NixOS Linux, DualCore, x86_64)
ghc 6.8.2
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2171#comment:8>
GHC <http://www.haskell.org/ghc/>
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