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{-# LANGUAGE ScopedTypeVariables #-}
-- !!! test threadDelay, Random, and QSemN.
-- start a large number (n) of threads each of which will wait for a
-- random delay between 0 and m seconds. We use a semaphore to wait
-- for all the threads to finish.
import System.Random
import Control.Concurrent
import Control.Exception
import Control.Monad
n = 5000 -- no. of threads
m = 3000 -- maximum delay
main = do
v <- newEmptyMVar
is <- replicateM n $ getStdRandom (randomR (1,m))
mapM_ (fork_sleep v) is
replicateM_ n (takeMVar v)
where
fork_sleep v i = forkIO $ do threadDelay (i*1000); putMVar v ()
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