Can't yield from within an instance created by reflection

[Ron Pressler]

I’d be interested to see how well this works with virtual threads, perhaps with a custom scheduler.
Should be very similar to using continuations directly.

As to continuations, the fact that they *can* work *some* of the time doesn’t mean we can expose them. Other
times, they can break compiler assumptions and result in undefined behaviour.

— Ron

> On 6 Apr 2021, at 16:42, Øystein Myhre Andersen <o.myhre at gmail.com> wrote:
> 
> 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.
>> 
>> 
>> 
>> 
>>