Jonathan Cast wrote:
On Mon, 2007-11-05 at 20:12 +0000, Andrew Coppin wrote:
Hi folks.
Take a look at this:
render :: IOArray Point Colour -> (Point -> Colour) -> IO ()
render framebuffer fn = mapM_ (\p -> writeArray framebuffer p (fn p))
all_points
How do I alter this to compute fn in multiple threads in parallel? (As
you can see from the type signature, the calculation is independent for
each pixel.)
You can spark a thread for each computation of fn, like such:
writeArray framebuffer p `parApp` fn p
where
parApp f x = x `par` f x
Hmm, that may be a little *too* fine-grained. (But then, just because I
spark 175,862 threads doesn't mean it will actually *run* that many at
once, right?) I guess I'll try it and see...
Or, alternatively, since I believe IOArray is lazy, you could grab a
list and hand it to parListChunk (from Parallel.Strategies) or there
abouts:
xn <- getElems framebuffer
evaluate $ parListChunk 100 rwhnf
or something (evaluate is from Control.Exception; rwhnf is also from
Parallel.Strategies).
Yes, IOArray is lazy. The *real* array type I'm using is unboxed and
therefore strict - however, the order in which pixels are written is of
no interest to me. I will sit and have a think about this one too.
Thanks.
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
