What I understand, Haskell have green threads. But how light weight are they. Is it possible to create 1 million threads?
Or How long would it take for 100 000 threads?
What I understand, Haskell have green threads. But how light weight are they. Is it possible to create 1 million threads?
Or How long would it take for 100 000 threads?
Well according to here the default stack size is 1k, so I suppose in theory it would be possible to create 1,000,000 threads - the stack would take up around 1Gb of memory.
from here.
import Control.Concurrent
import Control.Monad
n = 100000
main = do
left <- newEmptyMVar
right <- foldM make left [0..n-1]
putMVar right 0 -- bang!
x <- takeMVar left -- wait for completion
print x
where
make l n = do
r <- newEmptyMVar
forkIO (thread n l r)
return r
thread :: Int -> MVar Int -> MVar Int -> IO ()
thread _ l r = do
v <- takeMVar r
putMVar l $! v+1
on my not quite 2.5gh laptop this takes less than a second.
set n to 1000000 and it becomes hard to write the rest of this post because the OS is paging like crazy. definitely using more than a gig of ram (didn't let it finish). If you have enough RAM it would definitely work in the appropriate 10x the time of the 100000 version.
Using the benchmark here, http://www.reddit.com/r/programming/comments/a4n7s/stackless%5Fpython%5Foutperforms%5Fgoogles%5Fgo/c0ftumi
You can improve the performance on a per benchmark-basis by shrinking the thread stack size to one that fits the benchmark. E.g. 1M threads, with a 512 byte stack per thread, takes 2.7s
$ time ./A +RTS -s -k0.5k