[Haskell-cafe] Simplest way to move a ... `using` ... line into the IO monad?

[Brandon Allbery]

Yes, because `async` uses actual threads, not sparks like
`Control.Parallel.Strategies`.

On Fri, Oct 27, 2023 at 7:14 PM David Banas <capn.freako at gmail.com> wrote:

> After switching to `mapConcurrently` I’m getting this:
>
>   SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)
>
> Is that to be expected?
>
> -db
>
>
> On Oct 27, 2023, at 11:51 AM, Viktor Dukhovni <ietf-dane at dukhovni.org>
> wrote:
>
> On Fri, Oct 27, 2023 at 07:43:07PM +0100, Tom Ellis wrote:
>
> On Fri, Oct 27, 2023 at 11:36:53AM -0700, David Banas wrote:
>
> What is the simplest way to translate a non-monadic line of Haskell code,
> such as:
>
> res = map foo xs `using` parList rseq
>
> For use in the IO monad?
>
> This doesn’t work:
>
> res <- mapM fooM xs `using` parTraversable rseq
>
>
> The docs for Control.Parallel.Strategies say "The parallel tasks
> evaluated by a Strategy may have no side effects. For
> non-deterministic parallel programming, see Control.Concurrent."[1].
> So I guess you should look into Control.Concurrent[2].
>
>
> For a more friendly interface:
>
>
> https://hackage.haskell.org/package/async-2.2.4/docs/Control-Concurrent-Async.html
>
> If the number of concurrent tasks is reasonably modest, a good fit could
> be `mapConcurrently`.
>
> For much larger numbers of tasks, it is best to run the jobs at a
> bounded concurrency, which may bring a BoundedChan to which the items to
> process are written, another to which results are written and a set of
> threads that do the processing, repeatedly reading more data until the
> channel is drained.
>
> *The* book on subject is: https://simonmar.github.io/pages/pcph.html
>
> --
>    Viktor.
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-- 
brandon s allbery kf8nh
allbery.b at gmail.com
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