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|
{- parallel processing via threads
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Utility.Parallel where
import Common
import Control.Concurrent
import Control.Exception
{- Runs an action in parallel with a set of values, in a set of threads.
- In order for the actions to truely run in parallel, requires GHC's
- threaded runtime,
-
- Returns the values partitioned into ones with which the action succeeded,
- and ones with which it failed. -}
inParallel :: (v -> IO Bool) -> [v] -> IO ([v], [v])
inParallel a l = do
mvars <- mapM thread l
statuses <- mapM takeMVar mvars
return $ reduce $ partition snd $ zip l statuses
where
reduce (x,y) = (map fst x, map fst y)
thread v = do
mvar <- newEmptyMVar
_ <- forkIO $ do
r <- try (a v) :: IO (Either SomeException Bool)
case r of
Left _ -> putMVar mvar False
Right b -> putMVar mvar b
return mvar
|
