On Fri, Dec 19, 2008 at 9:27 AM, Paul Keir <pk...@dcs.gla.ac.uk> wrote:
> module Main where > > import Control.Concurrent > > fibs = 0 : 1 : zipWith (+) fibs (tail fibs) > > heavytask m = putMVar m (fibs !! 100000) Oh, also, heavytask is not very heavy at all. It just writes the thunk (fibs !! 100000) into the MVar. Not a single number is added in this thread. You probably meant to have the thread evaluate its argument _before_ writing it to the variable: heavytask m = putMVar m $! (fibs !! 100000) (Or more transparently) heavytask m = let answer = fibs !! 100000 in answer `seq` putMVar m answer But as per my other comments, you will not see a speedup (in fact, you will probably see some slowdown as two threads compete to compute the same value). Luke > > > main = do ms <- sequence $ replicate 2 newEmptyMVar > mapM_ (forkIO . heavytask) $ tail ms > heavytask $ head ms > ms' <- mapM takeMVar ms > mapM_ print ms' > > Regards, > Paul > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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