[Haskell-cafe] forkSequence, runPar, parallelize (was: Re: You are in a twisty maze of concurrency libraries, all different ...)
It appears there are several implementations existing on Hackage of the following function, in various disguises: runPar :: [IO a] - IO [a] the idea being that the IO computations are run in parallel, rather than sequentially. My own Streaming Component Combinators package contains a similar function, but somewhat generalized: class Monad m = ParallelizableMonad m where parallelize :: m a - m b - m (a, b) instance ParallelizableMonad IO -- implemented using forkIO instance ParallelizableMonad Identity -- implemented using par instance ParallelizableMonad Maybe -- implemented using par Would there be any interest in having this class packaged in a separate library? If so, can you sugest a better name or some additional functionality? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] forkSequence, runPar, parallelize (was: Re: You are in a twisty maze of concurrency libraries, all different ...)
On Wed, Dec 9, 2009 at 2:17 PM, Mario Blazevic mblaze...@stilo.com wrote: It appears there are several implementations existing on Hackage of the following function, in various disguises: runPar :: [IO a] - IO [a] the idea being that the IO computations are run in parallel, rather than sequentially. My own Streaming Component Combinators package contains a similar function, but somewhat generalized: class Monad m = ParallelizableMonad m where parallelize :: m a - m b - m (a, b) instance ParallelizableMonad IO -- implemented using forkIO instance ParallelizableMonad Identity -- implemented using par instance ParallelizableMonad Maybe -- implemented using par Would there be any interest in having this class packaged in a separate library? If so, can you sugest a better name or some additional functionality? A similar function that I'm fond of: forkExec :: IO a - IO (IO a) forkExec k = do result - newEmptyMVar _ - forkIO $ k = putMVar result return (takeMVar result) Although I don't think it can be generalized to non-IO monads. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] forkSequence, runPar, parallelize (was: Re: You are in a twisty maze of concurrency libraries, all different ...)
Antoine Latter wrote: A similar function that I'm fond of: forkExec :: IO a - IO (IO a) It's cute that forkExec already has a dual operation with just the right name (specialised to IO): join :: IO (IO a) - IO a ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] forkSequence, runPar, parallelize
A similar function that I'm fond of: forkExec :: IO a - IO (IO a) forkExec k = do result - newEmptyMVar _ - forkIO $ k = putMVar result return (takeMVar result) Although I don't think it can be generalized to non-IO monads. Antoine I can't test it right now, but wouldn't the following do the job in the Identity monad? forkExec :: Identity a - Identity (Identity a) forkExec k = let result = runIdentity k in result `par` return (Identity result) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] forkSequence, runPar, parallelize
On Wed, Dec 9, 2009 at 3:44 PM, Mario Blazevic mblaze...@stilo.com wrote: I can't test it right now, but wouldn't the following do the job in the Identity monad? forkExec :: Identity a - Identity (Identity a) forkExec k = let result = runIdentity k in result `par` return (Identity result) Since Identity is a newtype, would that be equivalent to result `par` result? The forkExec in the IO monad let's other computations keep going until I need the result from the forked computation. In a pure computation, I can already get the same result with `par` and laziness, right? Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] forkSequence, runPar, parallelize
It's a good thing then that forkExec and return are denotationally equal (though not operationally). Otherwise, I'd be worried. Matthew Brecknell wrote: Antoine Latter wrote: A similar function that I'm fond of: forkExec :: IO a - IO (IO a) It's cute that forkExec already has a dual operation with just the right name (specialised to IO): join :: IO (IO a) - IO a ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] forkSequence, runPar, parallelize
I can't test it right now, but wouldn't the following do the job in the Identity monad? forkExec :: Identity a - Identity (Identity a) forkExec k = let result = runIdentity k in result `par` return (Identity result) Since Identity is a newtype, would that be equivalent to result `par` result? The forkExec in the IO monad let's other computations keep going until I need the result from the forked computation. You're right, it doesn't seem to work the way I hoped. The equivalent function on Maybe monad works, though, so it is possible to write forkExec in monads other than IO. In a pure computation, I can already get the same result with `par` and laziness, right? Yes. The goal is to enable writing monadic parallel computations which work under any parallelizable monad. For example, I'm using it to run two trampolining producer/consumer coroutines in parallel. A large majority of interesting coroutines I have are completely agnostic with respect to the underlying monad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
