Re: [Haskell-cafe] Parallel executing of actions

On 16/04/2007, at 12:30, Mitar wrote:

Hi!

On 4/16/07, Bertram Felgenhauer wrote:

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Since all the threads block on a single MVar how do they run in parallel?

The idea is that before the threads block on the MVar, they run their action x to completion.

The rendering crashes. I will have to precompute the values in threads someway and then sequentially draw it? Any suggestion how to do that?

Could it be that you are launching 400x300=120.000 new threads all at once? If you are not doing it already, it would be sensible to implement some pooling of threads. This is what I use myself, don't worry about the unsafeness IF you know that the sequence of computations doesn't matter: \begin{code} unsafeParMapM :: (a -> IO b) -> [a] -> IO [b] unsafeParMapM f = return . parMap rwhnf (unsafePerformIO . f) unsafeParMapMn :: Integral bound => bound -> (a -> IO b) -> [a] -> IO [b] unsafeParMapMn max f xx = return (map (unsafePerformIO . f) xx `using` parListChunk (fromIntegral max) rwhnf) unsafeParSeqn :: Integral bound => bound -> [IO a] -> IO [a] unsafeParSeqn max cc = return ((map unsafePerformIO cc) `using` parListChunk (fromIntegral max) rwhnf) \begin{code}