On Fri, Dec 16, 2005 at 05:46:33PM +0100, Peter Eriksen wrote:
Here's the code:
module Main where
import Control.Concurrent import Control.Concurrent.STM import System.Random
worker :: Int -> TVar Int -> IO () worker id tv = do sleepingTime <- randomRIO (0, 50000) threadDelay sleepingTime putStr $ show id atomically $ barrier tv id worker id tv
You've got the barrier after the putStr, so there's nothing to make the first ten putStrs be in order. I think you need a non-updating barrier before the putStr and then an updating function after the putStr (to tell the next worker that it is free to print).
barrier :: TVar Int -> Int -> STM () barrier tv id = do passed <- readTVar tv if (passed `mod` 10 == id) then writeTVar tv (passed+1) else retry
move_along :: TVar Int -> Int -> STM () barrier tv id = do passed <- readTVar tv writeTVar tv (passed+1)
worker :: Int -> TVar Int -> IO () worker id tv = do sleepingTime <- randomRIO (0, 50000) threadDelay sleepingTime atomically $ barrier tv id putStr $ show id atomically $ move_along tv id worker id tv -- David Roundy