[Jprogramming] [Jbeta] J904 multithreading

[Raul Miller]

It would be nice, I imagine, if we eventually had a mechanism like

https://www.cprogramming.com/snippets/source-code/find-the-number-of-cpu-cores-for-windows-mac-or-linux

to set up a default number of threads.

-- 
Raul


On Sat, Apr 9, 2022 at 3:04 PM Henry Rich <henryhrich at gmail.com> wrote:
>
> The big news in J904 is multithreading.  J verbs can now be run in
> different cores, sharing the J global namespaces.
>
> [A version of J with limited support for multithreading was revealed
> last year by John Ference of Monument AI.  John's work was an important
> proof of concept, but the J904 version is an independent development
> using pthreads instead of OpenMP.  John has agreed with Jsoftware to
> give Jsoftware access to the code and testcases used in his work.  We
> have not used the code.]
>
> Two primitives support multithreading:
>
> (0 T. '')   creates a thread on a new core.  A thread running a verb is
> called a /task/. Even if you don't plan to create tasks, you should
> create threads to allow JE to use them for its own purposes.
>
> ([x] u t. '' y) executes ([x] <@:u y) as a task to produce a boxed
> result.  The thread that executed t. continues to run.  But the result
> is a special kind of box called a /pyx/.
>
> ['pyx' is Greek for box, and has been brought into English on occasion
> when a word has been needed for a special box.  The most recent such
> borrowing until now is for the box used by the Royal Mint to hold coins
> for assay.]
>
> A pyx looks on the outside like any other box.  You can pass it as an
> argument.  But as soon as you look inside it, your thread is blocked
> until the task producing the pyx's value has completed. Then you see the
> value, and your thread continues.
>
> Tasks share the global namespaces and thus can freely read, write, stomp
> on, and delete names visible to other tasks.
>
> We encourage you to experiment with threads and tasks.  We are sure that
> a layer of synchronizing primitives - semaphores, locks, and mutexes -
> will be needed, but we would like to get practical experience with tasks
> before we implement them.  Suggestions welcome.
>
> Henry Rich
>
>
>
>
>
>
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