Can't yield from within an instance created by reflection

[Øystein Myhre Andersen]

As mentioned, I have implemented Simula's class Simulation. I have run
simulations with up to a million processes. I have done this both with
platform threads and with Continuations.

The time consumption with platform threads increased exponentially
while Continuations only increased linearly.
Just so you know.


On Tue, Apr 6, 2021 at 5:10 PM Alan Bateman <Alan.Bateman at oracle.com> wrote:

> On 06/04/2021 15:29, Øystein Myhre Andersen wrote:
>
> That's a pity to remove such a basic feature. I am working on an open
> source project to implement Simula using Java. As you probably know, Simula
> was a great inspiration to James Gosling when he defined Java. Kristen
> Nygaard and Ole-Johan Dahl strongly believed that basic concepts were the
> thing. And I see Delimited Continuations as an important basic concept.
> Simula introduced Quasi-parallel systems to define discrete event
> simulation. You want to use it for virtual threads but it is possible that
> there are somebody out there who will use it for eg artificial
> intelligence. Why stop that opportunity - I will use it to implement Simula
> coroutines ( QPS Sequencing).
>
>
> By the way, I have also written an implementation that uses
> oversynchronized threads. Platform threads works well but virtual threads
> do not. There is something wrong there. I will return when it has been
> analyzed more thoroughly.
>
>
> If you are interested, the Simula project can be found here:
>    https://portablesimula.github.io/github.io/ <https://urldefense.com/v3/__https://portablesimula.github.io/github.io/__;!!GqivPVa7Brio!JNUrhq9WTpQQqmLyjbcrT062Xy0A2NUQvg5fZuffY9p7H9dOD130REg_AxisbmwmpA$>
>
> Thanks for the link to the project implements Simula coroutines.
>
> Delimited continuations is a powerful primitive but not one that this
> project plans to expose at this time. One significant issue is that
> yielding on one thread and continuing on another would break the invariant
> that Thread.currentThread() doesn't change in a thread of execution. Thread
> locals, lock ownership and several other features would break. There is
> also the issue as to whether the control flow would be just too advanced
> for many developers. It might be that generators or some other feature that
> will use thread-confined coroutines but for now, our focus is on virtual
> threads.
>
> -Alan.
>
>
>
>
>