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