2{-# LANGUAGE ConstraintKinds #-}
3{-# LANGUAGE FlexibleContexts #-}
4{-# LANGUAGE FlexibleInstances #-}
5{-# LANGUAGE GeneralizedNewtypeDeriving#-}
6{-# LANGUAGE InstanceSigs #-}
7{-# LANGUAGE MultiParamTypeClasses #-}
8{-# LANGUAGE UndecidableInstances #-} -- XXX
11-- Module : Streamly.Streams.Parallel
12-- Copyright : (c) 2017 Harendra Kumar
15-- Maintainer : harendra.kumar@gmail.com
16-- Stability : experimental
20module Streamly.Streams.Parallel
30 -- * Function application
39import Control.Concurrent (myThreadId)
40import Control.Exception (SomeException(..), throwIO)
41import Control.Monad (ap)
42import Control.Monad.Base (MonadBase(..), liftBaseDefault)
43import Control.Monad.Catch (MonadThrow, throwM)
44-- import Control.Monad.Error.Class (MonadError(..))
45import Control.Monad.IO.Class (MonadIO(..))
46import Control.Monad.Reader.Class (MonadReader(..))
47import Control.Monad.State.Class (MonadState(..))
48import Control.Monad.Trans.Class (MonadTrans(lift))
49import Data.Functor (void)
50import Data.IORef (readIORef, writeIORef)
51import Data.Maybe (fromJust)
52import Data.Semigroup (Semigroup(..))
53import Prelude hiding (map)
55import qualified Data.Set as Set
57import Streamly.Streams.SVar (fromSVar, fromStreamVar)
58import Streamly.Streams.Serial (map)
60import Streamly.Streams.StreamK (IsStream(..), Stream, mkStream, foldStream,
61 foldStreamShared, adapt)
62import qualified Streamly.Streams.StreamK as K
64#include "Instances.hs"
66-------------------------------------------------------------------------------
68-------------------------------------------------------------------------------
70{-# NOINLINE runOne #-}
73 => State Stream m a -> Stream m a -> Maybe WorkerInfo -> m ()
75 case getYieldLimit st of
77 Just _ -> runOneLimited st m0 winfo
82 liftIO $ decrementBufferLimit sv
83 foldStreamShared st yieldk single stop m
85 sv = fromJust $ streamVar st
88 incrementBufferLimit sv
90 sendit a = liftIO $ void $ send sv (ChildYield a)
91 single a = sendit a >> (liftIO $ sendStop sv winfo)
92 yieldk a r = sendit a >> go r
96 => State Stream m a -> Stream m a -> Maybe WorkerInfo -> m ()
97runOneLimited st m0 winfo = go m0
102 yieldLimitOk <- liftIO $ decrementYieldLimit sv
105 liftIO $ decrementBufferLimit sv
106 foldStreamShared st yieldk single stop m
107 else liftIO $ cleanupSVarFromWorker sv
109 sv = fromJust $ streamVar st
112 incrementBufferLimit sv
113 incrementYieldLimit sv
115 sendit a = liftIO $ void $ send sv (ChildYield a)
116 single a = sendit a >> (liftIO $ sendStop sv winfo)
117 yieldk a r = sendit a >> go r
119{-# NOINLINE forkSVarPar #-}
120forkSVarPar :: (IsStream t, MonadAsync m)
121 => SVarStopStyle -> t m a -> t m a -> t m a
122forkSVarPar ss m r = mkStream $ \st yld sng stp -> do
123 sv <- newParallelVar ss st
124 pushWorkerPar sv (runOne st{streamVar = Just sv} $ toStream m)
126 StopBy -> liftIO $ do
127 set <- readIORef (workerThreads sv)
128 writeIORef (svarStopBy sv) $ Set.elemAt 0 set
130 pushWorkerPar sv (runOne st{streamVar = Just sv} $ toStream r)
131 foldStream st yld sng stp (fromSVar sv)
133{-# INLINE joinStreamVarPar #-}
134joinStreamVarPar :: (IsStream t, MonadAsync m)
135 => SVarStyle -> SVarStopStyle -> t m a -> t m a -> t m a
136joinStreamVarPar style ss m1 m2 = mkStream $ \st yld sng stp ->
138 Just sv | svarStyle sv == style && svarStopStyle sv == ss -> do
139 pushWorkerPar sv (runOne st $ toStream m1)
140 foldStreamShared st yld sng stp m2
141 _ -> foldStreamShared st yld sng stp (forkSVarPar ss m1 m2)
143-- | XXX we can implement it more efficienty by directly implementing instead
144-- of combining streams using parallel.
145{-# INLINE consMParallel #-}
146{-# SPECIALIZE consMParallel :: IO a -> ParallelT IO a -> ParallelT IO a #-}
147consMParallel :: MonadAsync m => m a -> ParallelT m a -> ParallelT m a
148consMParallel m r = fromStream $ K.yieldM m `parallel` (toStream r)
151-- Different variants of parallel differ in how the combined stream ends:
153-- - - parallel - ends when all stream end
154-- parallelEndByFirst - parallel1 - ends when the first stream ends
155-- parallelEndByAny - parallel_ - ends when any stream ends
157-- | Polymorphic version of the 'Semigroup' operation '<>' of 'ParallelT'
158-- Merges two streams concurrently.
161{-# INLINE parallel #-}
162parallel :: (IsStream t, MonadAsync m) => t m a -> t m a -> t m a
163parallel = joinStreamVarPar ParallelVar StopNone
165-- This is a co-parallel like combinator for streams, where first stream is the
166-- main stream and the rest are just supporting it, when the first ends
169-- | Like `parallel` but stops the output as soon as the first stream stops.
172{-# INLINE parallelEndByFirst #-}
173parallelEndByFirst :: (IsStream t, MonadAsync m) => t m a -> t m a -> t m a
174parallelEndByFirst = joinStreamVarPar ParallelVar StopBy
176-- This is a race like combinator for streams.
178-- | Like `parallel` but stops the output as soon as any of the two streams
182{-# INLINE parallelEndByAny #-}
183parallelEndByAny :: (IsStream t, MonadAsync m) => t m a -> t m a -> t m a
184parallelEndByAny = joinStreamVarPar ParallelVar StopAny
186------------------------------------------------------------------------------
187-- Convert a stream to parallel
188------------------------------------------------------------------------------
190mkParallel :: (IsStream t, MonadAsync m) => t m a -> m (t m a)
192 sv <- newParallelVar StopNone defState
193 pushWorkerPar sv (runOne defState{streamVar = Just sv} $ toStream m)
196------------------------------------------------------------------------------
197-- Stream to stream concurrent function application
198------------------------------------------------------------------------------
200{-# INLINE applyParallel #-}
201applyParallel :: (IsStream t, MonadAsync m) => (t m a -> t m b) -> t m a -> t m b
202applyParallel f m = mkStream $ \st yld sng stp -> do
203 sv <- newParallelVar StopNone (adaptState st)
204 pushWorkerPar sv (runOne st{streamVar = Just sv} (toStream m))
205 foldStream st yld sng stp $ f $ fromSVar sv
207------------------------------------------------------------------------------
208-- Stream runner concurrent function application
209------------------------------------------------------------------------------
211{-# INLINE foldParallel #-}
212foldParallel :: (IsStream t, MonadAsync m) => (t m a -> m b) -> t m a -> m b
214 sv <- newParallelVar StopNone defState
215 pushWorkerPar sv (runOne defState{streamVar = Just sv} $ toStream m)
218{-# INLINE teeToSVar #-}
219teeToSVar :: (IsStream t, MonadAsync m) => SVar Stream m a -> t m a -> t m a
220teeToSVar svr m = mkStream $ \st yld sng stp -> do
221 foldStreamShared st yld sng stp (go svr m)
225 go sv m0 = mkStream $ \st yld sng stp -> do
228 incrementBufferLimit sv
230 -- XXX wait for Stop response event on exception channel,
231 -- drain the exception channel.
233 sendit a = liftIO $ do
234 -- XXX check for exceptions before decrement so that we do not
235 -- block forever if the child already exited with an exception.
236 decrementBufferLimit sv
237 void $ send sv (ChildYield a)
238 single a = sendit a >> (liftIO $ sendStop sv Nothing) >> sng a
239 yieldk a r = sendit a >> yld a (go sv r)
240 in foldStreamShared st yieldk single stop m0
242-- In case of folds the roles of worker and parent on an SVar are reversed. The
243-- parent stream pushes values to an SVar instead of pulling from it and a
244-- worker thread running the fold pulls from the SVar and folds the stream. We
245-- keep a separate channel for pushing exceptions in the reverse direction i.e.
246-- from the fold to the parent stream.
248-- NOTE: If we use fromSVar here it will kill the main computation (the parent)
249-- when the SVar goes away so we use fromStreamVar instead.
251{-# NOINLINE handleChildException #-}
252handleChildException :: SVar t m a -> SomeException -> IO ()
253handleChildException _sv e = do
255 -- void $ sendReverse sv (ChildStop tid (Just e))
258-- | Redirect a copy of the stream to a supplied fold and run it concurrently
259-- in an independent thread. The fold may buffer some elements. The buffer size
260-- is determined by the prevailing 'maxBuffer' setting.
265-- -----stream m a ---------------stream m a-----
270-- > S.drain $ S.tee (S.mapM_ print) (S.enumerateFromTo 1 2)
275-- Exceptions from the concurrently running fold are propagated to the current
276-- computation. Note that, because of buffering in the fold, exceptions may be
277-- delayed and may not correspond to the current element being processed in the
278-- parent stream, but we guarantee that the tap finishes and all exceptions
279-- from it are drained before the parent stream stops.
282-- Compare with 'tap'.
286tee :: (IsStream t, MonadAsync m) => (t m a -> m b) -> t m a -> t m a
287tee f m = mkStream $ \st yld sng stp -> do
288 -- Buffer size for the SVar is derived from the current state
289 sv <- newParallelVar StopNone (adaptState st)
290 -- XXX exception handling
291 -- XXX if we terminate due to an exception, do we need to actively
292 -- terminate the fold?
293 liftIO myThreadId >>= modifyThread sv
294 void $ doFork (void $ f $ fromStream $ fromStreamVar sv)
295 (svarMrun sv) (handleChildException sv)
296 foldStreamShared st yld sng stp (teeToSVar sv m)
298------------------------------------------------------------------------------
299-- Concurrent Application
300------------------------------------------------------------------------------
308-- | Parallel function application operator for streams; just like the regular
309-- function application operator '$' except that it is concurrent. The
310-- following code prints a value every second even though each stage adds a 1
316-- S.mapM (\\x -> threadDelay 1000000 >> print x)
317-- |$ S.repeatM (threadDelay 1000000 >> return 1)
324(|$) :: (IsStream t, MonadAsync m) => (t m a -> t m b) -> t m a -> t m b
325f |$ x = applyParallel f x
327-- | Parallel reverse function application operator for streams; just like the
328-- regular reverse function application operator '&' except that it is
333-- S.repeatM (threadDelay 1000000 >> return 1)
334-- |& S.mapM (\\x -> threadDelay 1000000 >> print x)
341(|&) :: (IsStream t, MonadAsync m) => t m a -> (t m a -> t m b) -> t m b
344-- | Parallel function application operator; applies a @run@ or @fold@ function
345-- to a stream such that the fold consumer and the stream producer run in
346-- parallel. A @run@ or @fold@ function reduces the stream to a value in the
347-- underlying monad. The @.@ at the end of the operator is a mnemonic for
348-- termination of the stream.
351-- S.foldlM' (\\_ a -> threadDelay 1000000 >> print a) ()
352-- |$. S.repeatM (threadDelay 1000000 >> return 1)
359(|$.) :: (IsStream t, MonadAsync m) => (t m a -> m b) -> t m a -> m b
360f |$. x = foldParallel f x
362-- | Parallel reverse function application operator for applying a run or fold
363-- functions to a stream. Just like '|$.' except that the operands are reversed.
366-- S.repeatM (threadDelay 1000000 >> return 1)
367-- |&. S.foldlM' (\\_ a -> threadDelay 1000000 >> print a) ()
374(|&.) :: (IsStream t, MonadAsync m) => t m a -> (t m a -> m b) -> m b
377------------------------------------------------------------------------------
379------------------------------------------------------------------------------
381-- | Async composition with strict concurrent execution of all streams.
383-- The 'Semigroup' instance of 'ParallelT' executes both the streams
384-- concurrently without any delay or without waiting for the consumer demand
385-- and /merges/ the results as they arrive. If the consumer does not consume
386-- the results, they are buffered upto a configured maximum, controlled by the
387-- 'maxBuffer' primitive. If the buffer becomes full the concurrent tasks will
388-- block until there is space in the buffer.
390-- Both 'WAsyncT' and 'ParallelT', evaluate the constituent streams fairly in a
391-- round robin fashion. The key difference is that 'WAsyncT' might wait for the
392-- consumer demand before it executes the tasks whereas 'ParallelT' starts
393-- executing all the tasks immediately without waiting for the consumer demand.
394-- For 'WAsyncT' the 'maxThreads' limit applies whereas for 'ParallelT' it does
395-- not apply. In other words, 'WAsyncT' can be lazy whereas 'ParallelT' is
398-- 'ParallelT' is useful for cases when the streams are required to be
399-- evaluated simultaneously irrespective of how the consumer consumes them e.g.
400-- when we want to race two tasks and want to start both strictly at the same
401-- time or if we have timers in the parallel tasks and our results depend on
402-- the timers being started at the same time. If we do not have such
403-- requirements then 'AsyncT' or 'AheadT' are recommended as they can be more
404-- efficient than 'ParallelT'.
407-- main = ('toList' . 'parallely' $ (fromFoldable [1,2]) \<> (fromFoldable [3,4])) >>= print
413-- When streams with more than one element are merged, it yields whichever
414-- stream yields first without any bias, unlike the 'Async' style streams.
416-- Any exceptions generated by a constituent stream are propagated to the
417-- output stream. The output and exceptions from a single stream are guaranteed
418-- to arrive in the same order in the resulting stream as they were generated
419-- in the input stream. However, the relative ordering of elements from
420-- different streams in the resulting stream can vary depending on scheduling
421-- and generation delays.
423-- Similarly, the 'Monad' instance of 'ParallelT' runs /all/ iterations
424-- of the loop concurrently.
428-- import qualified "Streamly.Prelude" as S
429-- import Control.Concurrent
431-- main = 'drain' . 'parallely' $ do
432-- n <- return 3 \<\> return 2 \<\> return 1
434-- threadDelay (n * 1000000)
435-- myThreadId >>= \\tid -> putStrLn (show tid ++ ": Delay " ++ show n)
438-- ThreadId 40: Delay 1
439-- ThreadId 39: Delay 2
440-- ThreadId 38: Delay 3
443-- Note that parallel composition can only combine a finite number of
444-- streams as it needs to retain state for each unfinished stream.
446-- /Since: 0.7.0 (maxBuffer applies to ParallelT streams)/
449newtype ParallelT m a = ParallelT {getParallelT :: Stream m a}
450 deriving (MonadTrans)
452-- | A parallely composing IO stream of elements of type @a@.
453-- See 'ParallelT' documentation for more details.
456type Parallel = ParallelT IO
458-- | Fix the type of a polymorphic stream as 'ParallelT'.
461parallely :: IsStream t => ParallelT m a -> t m a
464instance IsStream ParallelT where
465 toStream = getParallelT
466 fromStream = ParallelT
469 {-# SPECIALIZE consM :: IO a -> ParallelT IO a -> ParallelT IO a #-}
470 consM = consMParallel
473 {-# SPECIALIZE (|:) :: IO a -> ParallelT IO a -> ParallelT IO a #-}
476------------------------------------------------------------------------------
478------------------------------------------------------------------------------
480{-# INLINE mappendParallel #-}
481{-# SPECIALIZE mappendParallel :: ParallelT IO a -> ParallelT IO a -> ParallelT IO a #-}
482mappendParallel :: MonadAsync m => ParallelT m a -> ParallelT m a -> ParallelT m a
483mappendParallel m1 m2 = fromStream $ parallel (toStream m1) (toStream m2)
485instance MonadAsync m => Semigroup (ParallelT m a) where
486 (<>) = mappendParallel
488------------------------------------------------------------------------------
490------------------------------------------------------------------------------
492instance MonadAsync m => Monoid (ParallelT m a) where
496------------------------------------------------------------------------------
498------------------------------------------------------------------------------
500{-# INLINE bindParallel #-}
501{-# SPECIALIZE bindParallel :: ParallelT IO a -> (a -> ParallelT IO b) -> ParallelT IO b #-}
502bindParallel :: MonadAsync m => ParallelT m a -> (a -> ParallelT m b) -> ParallelT m b
503bindParallel m f = fromStream $ K.bindWith parallel (K.adapt m) (\a -> K.adapt $ f a)
505instance MonadAsync m => Monad (ParallelT m) where
509------------------------------------------------------------------------------
511------------------------------------------------------------------------------
513MONAD_APPLICATIVE_INSTANCE(ParallelT,MONADPARALLEL)
514MONAD_COMMON_INSTANCES(ParallelT, MONADPARALLEL)
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