Hello haskellers,
in past few days, a lot of stuff on concurrency went through
the conference. I'm trying to use posted things and my own.
They work, even in a context switching regime, but I can't
exploit all the CPU's on my computer. Always is "active"
just one thread and, thus, the computation is even slower
than having a sequential version. Below, you can find
my code - it computes nothing useful, it's been simplified
to test parallelism, nothing else. Where's my error?
Regards
Dusan
import Control.Concurrent
-- computes nothing too much useful, but takes a long time ;-)
sumAllSums [] = 0
sumAllSums l@(_:xs) = sumlist 0 l + sumAllSums xs
where sumlist res [] = res
sumlist sr (v:vs) = sumlist (sr+v) vs
main = do
putStrLn "Starting..."
mv1 <- newEmptyMVar
mv2 <- newEmptyMVar
t1 <- forkOS $ mkSum1 mv1
t2 <- forkOS $ mkSum2 mv2
tt mv1 mv2
forkOS $ do killThread t1
killThread t2
putStrLn "Done!"
where
mkSum1 mv = do
let res = sumAllSums [1..10000]
let ms1 = "Sum1: " ++ show res
seq (length ms1) (putMVar mv ms1)
mkSum2 mv = do
let res = sumAllSums [1..10001]
let ms2 = "Sum2: " ++ show res
seq (length ms2) (putMVar mv ms2)
tt mv1 mv2 = do
yield
mr1 <- tryTakeMVar mv1
case mr1 of
Just r1 -> do
yield
putStrLn r1
yield
r2 <- takeMVar mv2
putStrLn r2
Nothing -> do
mr2 <- tryTakeMVar mv2
case mr2 of
Just r2 -> do
yield
putStrLn r2
yield
r1 <- takeMVar mv1
putStrLn r1
Nothing -> tt mv1 mv2
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