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module Main (main) where
import System.Environment
import Control.Concurrent
import Control.Monad
-----------------------------------------------------------------------------
-- test MVar throughput between the main thread and a child thread
-- This test runs quite slowly on the threaded/SMP RTS vs. the normal RTS,
-- because the main thread and child thread are run by different OS threads,
-- so each MVar communication requires real OS thread switching.
--
-- Figures I get are about a factor of 10 difference in speed, at GHC 6.5.
main = chanTest 300000
chanTest :: Int -> IO ()
chanTest n = do
chan <- newEmptyMVar
forkIO (writer chan n)
reader chan n
reader chan 0 = return ()
reader chan n = do
takeMVar chan
reader chan (n-1)
writer chan 0 = return ()
writer chan n = do
putMVar chan ()
writer chan (n-1)
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